Lisa is 29, has a degree in geography and worked for a while in marketing. Then one day her career took a different tack. She became a secret agent.

In a film of her life, she would be recruited to the shady world of espionage by a chalky Oxbridge don or a mysterious man in a trilby. The reality is more mundane. “I was doing research on the internet about options for working in the public sector when I found an article about MI5,” Lisa says. “Then I found out more on its website and decided to apply.”

MI5, formally called the Security Service, is responsible for protecting the country from terrorism, espionage and anyone intent on stealing sensitive information or assets. Lisa’s role is necessarily opaque but, as an intelligence officer with seven years’ experience, her post involves managing a team that works to disrupt potential terrorist activity. She also briefs senior managers and external contacts.

“I like the variety of the work and the range of posting opportunities,” she says. “I also like the fact that I don’t always know which investigations will be the priority as it depends on the threat to national security and new intelligence leads.”

Important attributes for an intelligence officer include the ability to work as part of a team, plus communication and analytical skills. Discretion and integrity are also vital.

Training is thorough and ongoing. For new recruits it begins with a week’s induction, then a mix of tailored and general courses run by MI5.

“The organisation takes training seriously and sometimes supports people to complete external courses,” Lisa says. On similarities between her work and that of secret agents in TV dramas, she says: “There are elements that are true but they are dramas. Showing me, working at my desk, preparing documentation to be submitted to the Home Office to have an interception warrant authorised would not make riveting viewing.”

Assuming, then, that life is not all car chases and assignations with seductive foreign agents, does that mean she can tell her nearest and dearest about her work? No. Lisa says: “I can tell my partner when I’ve had a good or less good day. I just don’t go into details and he understands that.”

She says that the need for secrecy with family and friends was “a bit strange” at first. “But when I joined we were given a full briefing on what to say and why it’s important and that made it easier when I was asked about what I did.”

The service also arranges “family days” at Thames House, MI5’s London headquarters, to give relatives an understanding of where their family member works.

But as Lisa points out, having to keep quiet about aspects of one’s work is not exceptional. “Friends in the medical profession or the financial sector follow strict confidentiality codes.”

Perks are good. Thames House has an on-site gym, exercise classes and squash courts, and because Lisa has worked for MI5 for more than five years she gets 30 days’ holiday, plus bank holidays and extra “privilege” days. She says: “There’s a generous pension scheme, flexible working, depending on operational commitments, and performance-related annual salary increases.”

Anyone thinking of applying should have or be expecting a 2:1 honours degree or have substantial relevant experience. The starting salary is £24,250 plus benefits.

But perks count for little if Goldfinger is on your tail. Is Lisa ever in danger? She plays a straight bat. “The organisation takes the personal security of staff really seriously and we have regular updates and briefings depending on what area we work in.”

And no, she does not drive an Aston Martin.

www.mi5careers.gov.uk

Times Recommends

• Inspirational leadership
• How to get a new job
• The reluctant CEO