New Defence Secretary Gavin Williamson confessed last night to a fling that at one time threatened to end his marriage.

The rising Tory star, touted as a possible next party leader, admitted that the brief office romance with a former colleague was ‘a dreadful mistake’ but said his wife Joanne had forgiven him.

Mr Williamson, 41, who was made Defence Secretary following the resignation of Sir Michael Fallon over sexual harassment claims, insisted the relationship had not gone beyond kissing ‘a couple of times’.

It occurred before he embarked on a career in politics but he is understood to have revealed details to party officials when he first ran for selection as an MP more than a decade ago. He has also told Downing Street.

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Gavin Williamson admitted that the brief office romance with a former colleague ‘a dreadful mistake’ but said his wife Joanne (pictured) had forgiven him

Mr Williamson was made Defence Secretary by Theresa May (pictured) following the resignation of Sir Michael Fallon over sexual harassment claims

Mr Williamson told the Daily Mail he became involved with the married woman in 2004, while working as a manager at fireplace manufacturer Elgin & Hall in Yorkshire.

‘I had a good relationship with everyone I worked with, but with one person this started to develop into something more,’ he said. ‘We had to travel together and spent a lot of time in each other’s company, the relationship became flirtatious and a couple of times we shared a kiss.

‘It never went further than that, but this had a profound impact on us both and those close to us. It was a dreadful mistake and stopped as suddenly as it had started.

‘I know that this caused problems for her, as it did for me. And having to explain to Joanne what had happened was one of the most difficult conversations of my life. I’ll never truly understand how she found it in her heart to forgive me, but I tell myself every day how lucky I am to be with such an amazing person.’

Mr Williamson said he had decided to quit his job as he had not wanted a constant reminder of his infidelity.

Mrs Williamson, a former primary school teacher, gave birth to their first child in late 2004. It was not clear whether her husband’s fling took place while she was pregnant.

Mr Williamson is pictured with Sir Gordon Messenger, the Vice-Chief of the Defence Staff (left), and Colonel John Clark (right)

Mr Williamson said he had decided to quit his job as he had not wanted a constant reminder of his infidelity

The couple now have two daughters and the Defence Secretary stresses that his family is central to his life.

‘My family means everything to me and I almost threw it away… This incident nearly destroyed two marriages,’ he said.

‘It will always be part of my past, but has not stopped my wife and I from building a wonderful family together.

‘I no longer sell fireplaces and have built a career in politics. Family will always be central to what I do and what I believe in.

‘It was the experience of nearly losing mine that made me realise how much mine really matters to me.’ A year after the fling, Mr Williamson made his first attempt to become an MP.

He unsuccessfully contested Blackpool North and Fleetwood at the 2005 election. As part of the Tory selection process, candidates are asked to declare any peccadilloes from their past.

He became MP for South Staffordshire in 2010 and has had a rapid rise at Westminster. Theresa May appointed him as her Chief Whip on becoming Prime Minister in 2016 as a reward for helping her see off Boris Johnson’s bid for the Tory leadership.

Mr Williamson became the youngest Defence Secretary since the role was created during the Second World War, leap-frogging more experienced ministers to take the role in November

Mrs Williamson, a former primary school teacher, gave birth to their first child in late 2004. It was not clear whether her husband’s fling took place while she was pregnant

A year later, he helped to broker the deal with the Democratic Unionist Party to boost her fragile Parliamentary majority.

As Chief Whip, Mr Williamson was credited with quashing a leadership plot against Mrs May following her disastrous party conference speech last year.

Mr Williamson outed the ringleader – former Tory chairman Grant Shapps – in the Press and the attempted coup fizzled out.

He was also reported to have been among the senior advisers who told the Prime Minister that Sir Michael Fallon would have to resign over sleaze allegations.

Sir Michael became engulfed in the Westminster sex harasment scandal when a journalist told Downing Street he had attempted to kiss her during a lunch meeting. Mr Williamson then became the youngest Defence Secretary since the role was created during the Second World War, leap-frogging more experienced ministers to take the role in November.

Last night sources said Mr Williamson did not believe his revelation of a fling with a former colleague was a resignation matter and denied there had been any element of sexual harassment in their relationship, although he was senior to her at their firm.

Gavin Williamson statement in full: How I nearly destroyed two marriages Mr Williamson is pictured making his way into 10 Downing Street ‘My family means everything to me and I almost threw it away. ‘In 2004, I worked for a fireplace manufacturing company in Yorkshire. I was married to Joanne, who I met when we both attended Scarborough Sixth Form College. ‘Through work I often spent time away from home visiting customers. Sometimes, I would be accompanied by other employees. ‘I had a good relationship with everyone I worked with, but with one person this started to develop into something more. ‘We had to travel together and spent a lot of time in each other’s company, the relationship became flirtatious and a couple of times we shared a kiss. ‘It never went further than that, but this had a profound impact on us both and those close to us. It was a dreadful mistake and stopped as suddenly as it had started. ‘I know that this caused problems for her, as it did for me. And having to explain to Joanne what had happened was one of the most difficult conversations of my life. ‘I’ll never truly understand how she found it in her heart to forgive me, but I tell myself every day how lucky I am to be with such an amazing person. ‘Going back to work afterwards it could never feel the same as every day would remind me that I had let down the person I love more than anything. ‘Given those difficulties I left my employment selling fireplaces almost immediately. My employer was understanding and we parted on amicable terms. ‘This incident nearly destroyed two marriages. It will always be part of my past, but has not stopped my wife and I from building a wonderful family together. ‘I no longer sell fireplaces and have built a career in politics. Family will always be central to what I do and what I believe in. It was the experience of nearly losing mine that made me realise how much mine really matters to me.’ Advertisement

Mr Williamson was born to Labour-supporting parents Ray, a local government worker, and Beverley, a job centre worker, in Scarborough, North Yorkshire.

He met his future wife at Scarborough Sixth Form College before studying social sciences at Bradford University.

He was the national chairman of Conservative Students and became a county councillor in 2001.

He also co-owned a Staffordshire pottery firm and was managing director of an architectural design company. After he was elected an MP in 2010 he was prime minister David Cameron’s parliamentary private secretary for three years.

He was made a CBE for political and public service in Mr Cameron’s 2016 resignation honours list.

He pledged allegiance to Mrs May when she stood as leader.

As her Chief Whip, he was tasked with enforcing party discipline – this included keeping tabs on any misbehaviour by Tory MPs.

He forged a reputation for cunning and ruthlessness which saw him dubbed ‘the baby-faced assassin’. He was also notorious for keeping a pet Mexican tarantula, Cronus, in a glass box on his desk – earning him a rebuke from the Commons authorities.