The Troubles have thrown up many strange twists and turns, but the story of the gun-toting IRA woman who became a Conservative councillor must rank among the oddest.

Until this week, Maria Gatland was in charge of education in the south London borough of Croydon, a well-respected widow who runs a garden maintenance business.

Yet, as a girl called Maria McGuire, she was the lover of IRA chief David O'Connell, travelling with him on a republican arms-buying mission. "I agreed with the shooting of British soldiers and believed the more who were killed the better," she wrote.

It is possible to set out the two parts of her life and describe some of the events in it. It is also amazing to consider how for years she played a part in public life without her early history becoming known. When it did come out – revealed by a mischievous opponent – she was instantly propelled from office by a shocked Conservative Party.

Maria McGuire was one of the most exotic creatures within the IRA in the early days of the Troubles. Unlike the vast majority of IRA members, who were working class and from Belfast, she was from a well-off Dublin family. She studied languages at university in the Irish capital, where most young people recoiled from the violence in the north. There was no republicanism in her family but she made contact with the IRA's political wing, Sinn Fein.

The minute she walked through the door, some IRA leaders became fascinated by her: "I was young. I was pretty," she recalled. But they were also interested in the fact that she was well spoken and educated. "She appeared from nowhere and the leadership of the time was smitten by her," an IRA veteran recalled. "Because she was middle class and could speak foreign languages, they thought she was the sort of volunteer they would like to have. She was always immaculately dressed. She spoke with a cultured accent and was well educated." She was, however, unpopular with the IRA women, who resented the fact that she was given her own gun at a time when weapons were in short supply.

She would later write about her time in the IRA in the book To Take Arms: AYear In The Provisional IRA. While as far as is known she never actually fired a shot in anger, she moved in the organisation's upper echelons. She also had an affair with O'Connell, later chief-of-staff, who she reported was particularly enthusiastic about car bombs. "We were exploding four bombs a day," she wrote. Her book is extraordinarily frank about both the sex and the violence, combining kiss-and-tell with kiss-and-kill.

O'Connell took her to the Continent on an abortive mission to buy modern arms to replace old equipment. The old stuff would malfunction during gun battles, which she said was "particularly annoying for the really good snipers". Their travels took them to Zurich, Brussels, Amsterdam and Paris, but they constantly felt they were being followed. In France, McGuire wrote: "At one period I thought seriously about using my gun on one of our shadows."

She and O'Connell were horrified to find in a British newspaper an item saying he was believed to be on the Continent buying guns for the IRA. They fled back to Ireland where they were not arrested or questioned. Later news reports named her as his companion. But even when she appeared at a press conference and coolly announced that she and O'Connell had been abroad trying to buy arms, they were not arrested. She falsely denied, however, that they were having an affair, an issue which greatly absorbed the puritanical Ireland of the time. She remained active in the IRA for some months afterwards. But O'Connell was bested in internal power struggles with other IRA leaders – one of whom, she said, "made a very hesitant pass at me".

O'Connell's car bombs were causing death and destruction on the streets of Belfast. "I admit that at the time I did not connect with the people who were killed or injured in such explosions," she wrote. But she eventually realised that the IRA campaign was one of "total sterility", and could see no moral grounds for it.

Then a particularly horrific IRA bomb which caused many civilian casualties went off in Belfast, and she "wondered about the crippled and the injured and the lives that had been changed for ever". She decided to leave the IRA and head for England. Word reached her from the authorities that she would not be interrogated, and indeed that she would receive Special Branch cover. She told her story in a Sunday newspaper, recorded television interviews, and wrote her book. Since then, she was assumed to have vanished for ever until this week, when it was revealed that Maria McGuire of the IRA had somehow mutated into Maria Gatland of the Conservative Party.

What is known of much of her life since then is fragmentary. She said she moved in about 1986 to Croydon, where she met her late husband Mervyn, who ran a garden maintenance business. At that time she was "very, very fragile". She said she told him about her background, and that he looked after her as she went through two breakdowns. Her husband wanted to become a Conservative councillor but fell ill and eventually died.

This week she said of her republican experiences: "In retrospect, perhaps I should have brought it up, but it was such a long time ago. I hope I would be able to be accepted on my merits as a person who tried to rebuild my life. It was 30 years ago, it was a long time ago. I was not to any extent trying to cover up my tracks but to rebuild my life which was shattered. I wanted to get on with my life and give something back. I wanted to use my talents and skills."

She was elected to the council in 2002, more recently taking charge of Croydon's education committee. One who has had dealings with her at the council describes her as determined and forceful, articulate and prepared to defend what she believes in.

Her CV mentions her Irish background but unsurprisingly makes no reference to the IRA. Instead, she asserts that she "feels strongly that learning about democracy should be an integral part of a good education".

In the last paragraph of her book, Gatland recalls ringing her family while hiding England in 1972 and discussing her future. Her mother told her: "There are very few places left for you now." Gatland concluded the book with the sentence: "That, I know, is true." Neither she nor her mother could have dreamt for one moment that she would find, for so many years, sanctuary among the Conservatives of Croydon.

A life in brief

Born: Dublin 1948, and lived in the city's Churchtown district.

Family: Two brothers, one sister.

Education: St Anne's school, Dublin, then University College Dublin, where she studied English language and literature.

Career: Became a member of the IRA in the early 1970s. Her book, To Take Arms: a Year in the Provisional IRA, was published in 1973. In the late 1980s, she ran a garden maintenance centre with her husband in south London. Since 2002 she has been a Tory councillor in Croydon. She became the borough's cabinet member for education in 2006. Her former IRA membership was exposed this year.

She says: "I regret my actions – of course I do. It is something I have paid for since then and I am paying for now again."

She says: "It never entered my head for a second that she had been a member of the IRA. It is quite remarkable that Maria had felt that this wasn't going to come out at some time, particularly as she had written a book about her experiences. We do ask if they are a member of another party but how can you check up if somebody has a history like this?" – Mike Fisher, the leader of Croydon Council

Belfast Telegraph