Secrets, spy tools and a 110-year-old lemon are on show in an exhibition from Britain's MI5

LONDON (AP) — A desiccated 110-year-old lemon that played a key role in espionage history is one of the star attractions of a London exhibition drawn from the files of MI5, Britain’s domestic intelligence agency.

Compact spy cameras, microdots in a talcum powder tin and a briefcase abandoned by fleeing Soviet spy Guy Burgess are also part of the show at Britain’s National Archives, which charts the history of a secretive agency that is – slowly – becoming more open.

MI5 Director General Ken McCallum told journalists at a preview on Tuesday that the organization’s work “is often different from fiction, whether that fiction is George Smiley or Jackson Lamb” – the brilliant spymaster of John le Carré's novels and the slovenly supervisor of MI5 rejects in Mick Herron’s “Slow Horses” series.

Many stories told in the exhibition, however, would not be out of place in a thriller.

The lemon, now black and shriveled, helped convict Karl Muller, a German spy in Britain during World War I. It was found by police in his dressing-table drawer, along with another in his overcoat pocket. Evidence at his secret trial showed their juice had been used to write invisible-ink letters detailing British troop movements.

Muller was executed by firing squad at the Tower of London in 1915.

In a coda that would not be out of place in “Slow Horses,” MI5 pretended Muller was still alive and wrote to his German handlers to ask for more money.

“The Germans duly sent more funds and MI5 used the funds to purchase a car,” exhibition curator Mark Dunton said. “And they christened the car ‘The Muller.’

“They then were reprimanded by the Treasury for unauthorized use of expenditure," he added.

The show includes declassified records held by the National Archives and items loaned from the secret museum inside Thames House, MI5’s London headquarters.

It charts the changing role of an agency that was founded in 1909 as the Secret Service Bureau with an initial staff of two officers.

There are records of its World War II successes, when the agency used captured Nazi agents to send disinformation back to Germany, deceiving Adolf Hitler about the location of the looming Allied invasion in 1944.

Failures include the years-long betrayal of the upper-crust “Cambridge Spies,” whose members spilled secrets to the Soviet Union from the heart of the U.K. intelligence establishment. Recently declassified MI5 documents on display include the 1963 confession of Cambridge spy Kim Philby, who denied treachery for years before he was exposed and fled to Moscow.

The exhibition also reveals changing attitudes, not least to women. The exhibition includes a 1945 report by spymaster Maxwell Knight discussing whether women could make good agents.

“It is frequently alleged that women are less discreet than men,” he noted, but declared that it was not so, saying that in “hundreds of cases of ‘loose talk’” most of the offenders were men.

There are admissions of past mistakes. The exhibition notes that MI5 was slow to recognize the threat from fascism in the 1930s, and later spent too much time spying on the small Communist Party of Great Britain. MI5 didn’t need to break into the party’s offices – it had a key, which is on display.

There are only a few items from the past few decades, showing how MI5’s focus has shifted from counterespionage to counterterrorism. Displays include a mortar shell fired by the Irish Republican Army at 10 Downing St. in 1991 while Prime Minister John Major was holding a Cabinet meeting.

MI5 only began releasing records to the U.K.’s public archives in 1997, generally 50 years after the events have passed. Even now, it controls what to release and what to keep secret.

“It would be a mistake to assume everything is in the exhibition,” said author Ben Macintyre, whose books on the history of intelligence include “Operation Mincemeat” and “Agent Zigzag.” But he said it still marks “a real sea-change in official secrecy.”

“A generation ago, this stuff was totally secret,” he said. “We weren’t even allowed to know that MI5 existed.”

“MI5: Official Secrets” opens Saturday and runs through Sept. 28 at the National Archives in London. Admission is free.

A National Archives staff member looks at a 1910 Enseignette camera, the first spy camera purchased by MI5, during a preview for the MI5: Official Secrets exhibition at the National Archives in London, Tuesday, April 1, 2025. (Jonathan Brady/PA via AP)

A Yardley talcum powder tin from 1960 used by one of the Portland spies to conceal microdot equipment on display during a preview for the MI5: Official Secrets exhibition at the National Archives in London, Tuesday, April 1, 2025. (Jonathan Brady/PA via AP)

The Krogers' 'flash transmission' radio equipment, 1960, on display during a preview for the MI5: Official Secrets exhibition at the National Archives in London, Tuesday, April 1, 2025. (Jonathan Brady/PA via AP)

The lemon used for writing in invisible ink, produced in evidence at Karl Muller's trial, 1915, on display during a preview for the MI5: Official Secrets exhibition at the National Archives in London, Tuesday, April 1, 2025. (Jonathan Brady/PA via AP)

A copy of the German War Merit Cross 'Kriegsverdienstkreuz', 1939 on display during a preview for the MI5: Official Secrets exhibition at the National Archives in London, Tuesday, April 1, 2025. (Jonathan Brady/PA via AP)

MI5 staff list on display during a preview for the MI5: Official Secrets exhibition at the National Archives in London, Tuesday, April 1, 2025. (Jonathan Brady/PA via AP)

Director General of MI5, the UK's Security Service, Ken McCallum, during a preview for the MI5: Official Secrets exhibition at the National Archives in London, Tuesday, April 1, 2025. (Jonathan Brady/PA via AP)

A National Archives staff member looks at an example of an instant camera and bottle used to make a bomb, recreated as evidence by the Bomb Data Centre, on display during a preview for the MI5: Official Secrets exhibition at the National Archives in London, Tuesday, April 1, 2025. (Jonathan Brady/PA via AP)

Guy Burgess' passport on display during a preview for the MI5: Official Secrets exhibition at the National Archives in London, Tuesday, April 1, 2025. (Jonathan Brady/PA via AP)

EA National Archives member of staff looks at a Britain First report of Mosley's speech at Earl's Court, 16 July 1939, left, and a British Union of Fascists armband, right, during a preview for the MI5: Official Secrets exhibition at the National Archives in London, Tuesday, April 1, 2025. (Jonathan Brady/PA via AP)

National Archives staff members look at facets of a recreation of the double cross operation room which was headed up by the XX committee circa 1944, during a preview for the MI5: Official Secrets exhibition at the National Archives in London, Tuesday, April 1, 2025. (Jonathan Brady/PA via AP)

Director General of MI5, the UK's Security Service, Ken McCallum, during a preview for the MI5: Official Secrets exhibition at the National Archives in London, Tuesday, April 1, 2025. (Jonathan Brady/PA via AP)

National Archives staff members look at facets of a recreation of the double cross operation room which was headed up by the XX committee circa 1944, during a preview for the MI5: Official Secrets exhibition at the National Archives in London, Tuesday, April 1, 2025. (Jonathan Brady/PA via AP)

Guy Burgess' passport and briefcase on display during a preview for the MI5: Official Secrets exhibition at the National Archives in London, Tuesday, April 1, 2025. (Jonathan Brady/PA via AP)

National Archives staff members look at facets of a recreation of the double cross operation room which was headed up by the XX committee circa 1944, during a preview for the MI5: Official Secrets exhibition at the National Archives in London, Tuesday, April 1, 2025. (Jonathan Brady/PA via AP)

KYIV, Ukraine (AP) — Russia launched a second major drone and missile bombardment of Ukraine in four days, officials said Tuesday, aiming again at the power grid and apparently snubbing U.S.-led peace efforts as the war approaches the four-year mark.

Russia fired almost 300 drones, 18 ballistic missiles and seven cruise missiles at eight regions overnight, Ukrainian President Volodymyr Zelenskyy said on social media.

One strike in the northeastern Kharkiv region killed four people at a mail depot, and several hundred thousand households were without power in the Kyiv region, Zelenskyy said. The daytime temperature in the capital was -12 C (around 10 F). The streets were covered with ice, and the city rumbled with the noise from generators.

Four days earlier, Russia also sent hundreds of drones and dozens of missiles in a large-scale overnight attack and, for only the second time in the war, it used a powerful new hypersonic missile that struck western Ukraine in what appeared to be a clear warning to Kyiv’s NATO allies that it won’t back down.

On Monday, the United States accused Russia of a “ dangerous and inexplicable escalation ” of the fighting, when the Trump administration is trying to advance peace negotiations.

Tammy Bruce, the U.S. deputy ambassador to the United Nations, told an emergency meeting of the U.N. Security Council that Washington deplores “the staggering number of casualties” in the conflict and condemns Russia’s intensifying attacks on energy and other infrastructure.

Russia has sought to deny Ukrainian civilians heat and running water in the freezing winter months over the course of the war, hoping to wear down public resistance to Moscow’s full-scale invasion, which began on Feb. 24, 2022. Ukrainian officials describe the strategy as “weaponizing winter.”

In Ukraine’s Kharkiv region, the Russian attack also wounded 10 people, local authorities said.

In the southern city of Odesa, six people were wounded in the attack, said Oleh Kiper, the head of the regional military administration. The strikes damaged energy infrastructure, a hospital, a kindergarten, an educational facility and a number of residential buildings, he said.

Zelenskyy said that Ukraine is counting on quicker deliveries of agreed upon air defense systems from the U.S. and Europe, as well as new pledges of aid, to counter Russia’s latest onslaught.

Meanwhile, Russian air defenses shot down 11 Ukrainian drones overnight, Russia’s Ministry of Defense said Tuesday. Seven were reportedly destroyed over Russia’s Rostov region, where Gov. Yuri Slyusar confirmed an attack on the coastal city of Taganrog, about 40 kilometers (about 24 miles) east of the Ukrainian border, in Kyiv's latest long-range attack on Russian war-related facilities.

Ukraine’s military said domestically-produced drones hit a drone manufacturing facility in Taganrog. The Atlant Aero plant carries out design, manufacturing and testing of Molniya drones and components for Orion unmanned aerial vehicles, according to the General Staff of the Armed Forces of Ukraine. Explosions and a fire were reported at the site, with damage to production buildings confirmed, the General Staff said.

It wasn't possible to independently verify the reports.

Katie Marie Davies contributed to this report from Manchester, England.

Follow AP’s coverage of the war in Ukraine at https://apnews.com/hub/russia-ukraine

In this photo provided by the Ukrainian Emergency Service, emergency services personnel work to extinguish a fire following a Russian attack in Kharkiv, Ukraine, Tuesday, Jan. 13, 2026. (Ukrainian Emergency Service via AP)

In this photo provided by the Ukrainian Emergency Service, emergency services personnel work to extinguish a fire following a Russian attack in Kharkiv, Ukraine, Tuesday, Jan. 13, 2026. (Ukrainian Emergency Service via AP)

In this photo provided by the Ukrainian Emergency Service, emergency services personnel work to extinguish a fire following a Russian attack in Kharkiv, Ukraine, Tuesday, Jan. 13, 2026. (Ukrainian Emergency Service via AP)

In this photo provided by the Ukrainian Emergency Service, emergency services personnel work to extinguish a fire following a Russian attack in Kharkiv, Ukraine, Tuesday, Jan. 13, 2026. (Ukrainian Emergency Service via AP)

In this photo provided by the Ukrainian Emergency Service, emergency services personnel work to extinguish a fire following a Russian attack in Kyiv region, Ukraine, Tuesday, Jan. 13, 2026. (Ukrainian Emergency Service via AP)