Stella Rimington was formerly head of MI5 before turning to writing. A couple of non-fiction works appeared before she turned her hand to fiction
An educated guess, as I haven't read any of her 9 book long Liz Carlyle series yet, but I would imagine they might closely depict the average working life of a British intelligence officer in the post-Cold War era. Hopefully not too closely, as I would imagine, like most jobs there are plenty of days where boredom is the norm.
The full series list is
1. At Risk (2004)
2. Secret Asset (2006)
3. Illegal Action (2007)
4. Dead Line (2008)
5. Present Danger (2009)
6. Rip Tide (2011)
7. The Geneva Trap (2012)
8. Close Call (2014)
9. Breaking Cover (2016)
From her author page at Fantastic Fiction........
Stella Rimington joined the Security Service (MI5) in 1965 and during her career she worked in all the main fields of the Service's responsibilities - counter-subversion, counter-espionage and counter-terrorism - and became successively Director of all three branches. She was appointed Director-General of MI5 in 1992. She was the first woman to hold the post and the first Director-General whose name was publicly announced on appointment.
Present Danger (2009)
MI5 intelligence officer Liz Carlyle has just been despatched to Northern Ireland. It's a promotion, and she'll be running agents - her favourite activity - but it also means being separated from Charles Wetherby, her old boss, recently widowed and a very close friend. Attachments in the Intelligence Services are not encouraged: it seems her superiors know more about Liz's life than she thinks. In Belfast, Liz and her team are monitoring the brutal breakaway Republican groups who never accepted the peace process and want to continue their 'war'. Intelligence is focused on the shady Fraternity, with links to drug-running, arms-dealing and organised crime. With some help from Special Branch and a volunteer informant who seems to be legit, the Fraternity's leader is identified as a cold, calculating and ruthless American, hijacking the Cause for his own financial ends. It is a perilous group to become involved with. Especially if your informant turns tail...
Close Call (2014)
The Arab Spring has swept through the Middle East and Liz Carlyle and her compatriots in the Thames House's counter-espionage division are racing to investigate arms deals in Yemen. There's a UN embargo forbidding any member country from supplying arms to either side in the uprisings, but Andy Bokus, head of the CIA's London Station, has evidence that the weapons being smuggled into Yemen are not only being sold to both sides, but are coming from a connection in the UK--a highly embarrassing black mark on the government and, if true, full of disastrous consequences.
British-American cooperation widens as Liz teams up with her old rival Bruno McKay, MI6's Head of Station in Paris, and Isobel Florian of the French domestic service, the DCRI, to trail and trap the elusive weapons dealer. The evidence points to a former French intelligence officer, Antoine Milraud, who leads them all on a mad chase across Europe until investigators witness him passing something to an elegantly dressed, very mysterious man.
When Milraud is caught and informs on his fellow conspirators, Liz finds herself embroiled in a larger, potentially explosive situation that twists all the way back to what she feared most--that the arms are being sold through the UK, and the mysterious man is closer and more capable of brutal violence than she ever could have imagined.