Fellow Conservative MPs call Gavin Williamson the “baby-faced assassin” – a nickname that can only be enhanced by his extraordinary rise to Defence Secretary.

Strikingly, the 41-year-old has been appointed after apparently playing a key role in the sacking of his predecessor Michael Fallon, as the sex pest scandal grips Westminster.

Some now believe the father-of-two, with a bedrock of support among Tory MPs, can go all the way to No 10 – but others believe his star will fade in the new glare of publicity.

Williamson is a Northerner, the son of Labour voters and a state-educated graduate of the University of Bradford – in stark contrast to the Oxbridge-dominated Conservative benches.

A national chairman of Conservative Students – before its extremism forced it to be wound up, in 1998 – he worked in the Staffordshire pottery industry before becoming an MP.

With those local roots put down, he won the safe South Staffordshire seat in 2010 and, within three years, had grabbed the powerful role of unpaid aide to David Cameron.

However, his rapid ascent is explained by his astute decision to nail his colours firmly to Theresa May’s mast in the frantic days that followed the Brexit referendum result, in June 2016.

After Cameron’s fall, Boris Johnson looked the coming man – but Williamson phoned May and told her he wanted to help steer her campaign.

He later wrote: “Everyone told me I was wrong and that she couldn’t possibly win, but I sensed the mood of the country.

“People were looking for someone who is a serious politician who can make tough decisions in challenging times. I just knew instinctively that she was the one.”

Within 24 hours, he was the future prime minister’s campaign manager – an appointment that left him “absolutely flabbergasted”, he later said – and within weeks he was Chief Whip.

Nearly a year later, May again found herself in Williamson’s debt, as she scrambled to stay in Downing Street after her general election debacle.

It was the Chief Whip who nailed down the £1bn “cash for votes” deal with the Democratic Unionist Party, which now props her up in power.

Since then, he has hit the headlines after revealing he keeps a pet tarantula on his desk, which he has threatened to launch on rebellious Tory MPs.

Sharing a picture of the terrifying-looking Cronus on his Instagram account, Williamson joked: “Just finished packing everything I need for #conservativepartyconference.”

It is worth noting that, in Greek mythology, tough guy Cronus castrated and killed his own father – before eating his own children because he feared they would overthrow him.

Given that Williamson’s job is to prevent the embarrassing loss of Commons votes, he is clearly failing in that. The Tories now regularly accept defeat on Labour motions – including, this week, on the release of secret Brexit studies.

However, that is a reflection of May’s own weakness and the extent to which she relies on him is illustrated by Wednesday night’s dramatic events.

Williamson is said to have warned the Prime Minister there could be further allegations about Fallon’s behaviour and advised that he should be fired.

The very next day, Williamson has replaced the fallen Fallon as Defence Secretary – like his boss, a Remainer who must now help drive through Brexit.

One opinion is that he is a poor speaker and “a bit goofy”, but he has also been praised as hardworking, helpful, honest and friendly.