Teddy Young, a 24-year-old Royal Navy service member, has been charged with spying. Between November 2024 and May 2025, he stands accused of copying classified material with the intention of handing it to an unnamed foreign power.

With the Ukraine war raging, overseas intelligence agencies will be working flat-out to recruit agents and gather information about Britain’s intent and capabilities. The challenge facing MI5, which leads the UK’s counter-espionage effort, is greater than ever. An eternal question remains: why do people choose to betray their country and spy for an enemy state?

At this early stage, Young’s motivations are unclear. It is useful, though, to look at this week’s other espionage story, concerning the former German spy chief, August Hanning, who has been arrested on suspicion of treason after being accused of leaking state secrets.

Hanning had already left government service in 2009 to work as an attorney and legal consultant when his alleged skulduggery began. Between 2010 and 2022, he is said to have paid his former chief of staff undisclosed sums for over 2,000 pieces of intelligence material. It seems obvious that some of this would have been used for his consultancy work. That is still espionage, of course, of a more insidious kind — insiders trading on contacts to share classified material. But Hanning is alleged to have used this information to draft an “analysis” for a foreign intelligence service.

It’s worth remembering that espionage is the second-oldest profession, and spies sell themselves for a host of reasons. The classic image of the spy involves individuals driven by ideological difference, such as the Cambridge Five who were recruited by the Soviets in the Thirties and provided valuable wartime intelligence.

For many other spies, though, the reasons are often more prosaic — and financial. Hanning is known to have had significant financial difficulties since 2021 because of the collapse of a Latvian bank on whose board he served. Likewise, a Bulgarian spy ring convicted last year had monitored and plotted against journalists and Russian dissidents on an “industrial scale”, and were in line to receive almost £1 million in payments.

Rigorous vetting of officers to spot financial risks and monitoring to spot any sudden changes in lifestyle can reduce the risk, but not in every case. Aldrich Ames, the KGB asset at the CIA, bought a $540,000 house for cash in 1989, as well as a Jaguar sports car and a farm in Colombia. Having previously been hard-up, he was spending $30,000 a month on credit cards.

Likewise, vigilance can help to spot spies motivated by grudges. David Smith, the British Embassy security guard in Berlin who was jailed in 2023 after selling secrets to Russia, said he felt disgruntled at his employer for making him come into work during the pandemic when others were at home on full pay. After his Ukrainian wife left him, he fell into alcoholism and depression and became overtly anti-British and anti-German, collecting Russian memorabilia.

Harder to spot is when an officer becomes trapped, often in sexual situations, and is then bribed into spying to avoid being outed to the Foreign Office. When I arrived in Moscow, the security officer leaned conspiratorially across the table during our introductory chat. Lowering his voice, he said: “If you’re stupid enough to think about trading up with a Russian woman, then you’ll have to tell your wife. But before you do that, tell me!”

It’s for this reason that, like every middle-aged colleague, I was advised to look in the “ugly mirror” every day. This would serve as a reminder that if an attractive Russian found me the most interesting man on the planet, it wouldn’t be for my looks. During my time in Moscow, two officers were sent home at a moment’s notice, one of whom left the service shortly afterwards. In addition to rigorous security vetting, every embassy has an in-house security officer — a sizable team in larger embassies — to keep an eye on the diplomats and the local staff. There is no cure for spying, only treatment.

We are spying and being spied on, all of the time, and it is the job of MI5 to counter that threat. The Teddy Young case provides a vivid reminder that even people we think we can trust will sometimes betray us.