Chris Mason: Natalie Elphicke's defection to Labour was one barely anyone saw coming

Keir Starmer with Natalie Elphicke in his parliamentary office

It all happened pretty quickly and barely anyone in Westminster saw it coming.

Rishi Sunak, I'm told, only found out about Natalie Elphicke's defection moments before Prime Minister's Questions.

Some senior Conservatives, when they first got wind she was leaving, assumed she was joining Reform UK.

Natalie Elphicke's very discreet conversations with Labour had gone on for a few weeks.

A key connection she had on Labour's benches - going back a decade-and-a-half - was with John Healey.

Mr Healey, who accompanied her into Parliament as she took up her seat on the Labour benches, was housing minister when Labour were last in government.

Ms Elphicke has had a professional interest in housing policy for years, well before she became an MP - and emphasised this interest in the statement she released accompanying her defection.

She was awarded an OBE for her housing work in 2015.

Conservative MPs are baffled by it all.

One party figure said recent campaign leaflets sent out in her name - and talked up by voters in Dover as looking glossy and expensive - were all about the Conservative approach to illegal immigration and their view that Labour's policy on it is hopeless.

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"Staggered" and "poisonous" are two other words I've scribbled into my notebook from senior Tories.

Among Labour MPs, the language is just as colourful.

Some are baffled. Others are plain angry.

Some struggle with her positions on policy.

But for others it is remarks she made to The Sun after her ex-husband's conviction for sexual assault that have left them angry and upset.

The newspaper reported her as having said Charlie Elphicke - the former Conservative MP for what is now her seat - was "attractive" and "attracted to women" and that had made him an "easy target".

She has not commented on those remarks.

Labour said "all those issues have been dealt with previously both in Parliament and in public".

But one senior figure suggested to me their new MP would find a moment to address Labour MPs with concerns about what she had said.

It seems likely she will need to, given the depth of the anger from some of her new colleagues.

Privately, Labour and Conservative figures are pointing out that while Diane Abbott remains outside the Parliamentary Labour Party, Natalie Elphicke now sits within it.

But others on Labour's benches say, ultimately, this is about the bigger picture.

Luring another Conservative MP to join them, just 10 days after the last one, says everything, they hope, about their momentum and the Conservatives' lack of it.

But her arrival has proved far less than straightforward to many in her new party.

Listen to Chris on BBC Newscast on the shock defection of another MP from the Tories to Labour.