Former Home Secretary Priti Patel has announced she's backing Boris Johnson for Prime Minister, as he returns from his holiday in the Caribbean.

The 58-year-old was ousted from Downing Street earlier this year but replacement Liz Truss lasted just six weeks after winning the leadership contest.

Her resignation has triggered a new leadership election, which requires prospective candidates to receive the backing of at least 100 of the 357 Conservative MPs.

Rishi Sunak, who lost to Truss in the previous contest, is the favourite and is believed to already have the requisite number of backers.

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But with Mr Johnson flying back from his holiday in the Caribbean it's expected he'll formally announce a challenge, and his former Home Secretary has publicly backed him.

Ms Patel wrote on Twitter: "Boris has the mandate to deliver our elected manifesto and a proven track record getting the big decisions right. I’m backing him in the leadership contest.”

That takes Mr Johnson to around 47 backers, with Penny Mordaunt, the only candidate to officially announce a run, on around 21.

At this stage though most MPs have not made a public pledge of support to any candidate.

Mr Johnson and his family landed back in the UK from a holiday in the Dominican Republic at around 20 past 10 this morning.

The flight was being tracked by around 7,000 users of the FlightRadar24 website.