Image copyright Reuters Image caption Rishi Sunak became chancellor after Boris Johnson's cabinet reshuffle

Four weeks ago, Rishi Sunak had no idea he would be delivering the Budget on 11 March. Then Sajid Javid resigned, Mr Sunak was promoted to chancellor and the stage was set.

In between making cups of tea, he has been given little time to prepare for the biggest day in a chancellor's calendar.

He is not the first person to be thrown into the spotlight at the last minute. So from which replacements, stand-ins and substitutes can he take inspiration or warning?

Strictly unintended

Kelvin Fletcher was at home when his agent called to say that he was wanted as a late replacement on Strictly Come Dancing.

He was approached after Made In Chelsea star Jamie Laing, part of the planned line-up, had been injured in training.

Contracts were sent within an hour, he was soon on the phone to producers, and the next day he had a medical.

Image caption Kelvin Fletcher was a late replacement on Strictly, then won

"I got to rehearse for, I think, a week or so. And then it was the opening night," the ex-Emmerdale actor said.

"I wasn't expecting the call. I never thought it was an option. It couldn't have been any more of a curveball than it was."

Of course, the 36-year-old went on to win and lift the glitterball trophy with partner Oti Mabuse in front of 11 million viewers.

'I blagged it'

There are late replacements and there are really late replacements.

Steph Parry was sitting in the dressing room of a London theatre, ready for a different show, when she received a call from the general manager of Mamma Mia! being staged down the road.

He told her that the lead had been forced off stage with a calf injury during the opening scene of the show. Within just 18 minutes of the show being halted, she was on the stage playing Donna Sheridan, the role Meryl Streep played in the Mamma Mia! film.

Image copyright Steph Parry Image caption Steph Parry said she did not have time to worry about performing

"I didn't have time to worry, I just needed a wee! I remember sitting on the loo thinking about the lines for the next scene," she said, having previously been in the show.

"After that, I had no need to think, I just had to trust that it was somewhere in the back of my mind. It was worse, the more I thought about [it]!

"The choreography was the biggest wing in the whole of my life - I blagged it!"

The accidental substitute

Guy Goma was at the BBC for a job interview. He was not there to be interviewed live on television.

He was, however, interviewed live on television, with legendary results.

Media playback is unsupported on your device Media caption Guy Goma: BBC's best/worst interview?

The other awkward substitution

Chancellor Rishi Sunak is a football fan. One of his childhood heroes was Southampton football player Matt Le Tissier.

In November 1996, legendary Saints player Le Tissier was injured and substituted with one of the club's most infamous players - Ali Dia.

Incredibly, amateur Dia had been signed on a one-month contract, apparently after he was recommended to manager Graeme Souness by a man claiming to be the then-world player of the year, George Weah.

Even more incredibly, Souness brought him on in the Premiership (now Premier League) match against Leeds. He lasted 53 minutes before being replaced himself. He was never seen in a Southampton shirt again.

The manager later said he knew he was a dud, but his squad was depleted by injury. Le Tissier said: "He ran around the pitch like Bambi on ice."

Hours, not weeks, to prepare for a Budget

Mr Sunak has had four weeks to get ready for the Budget after his predecessor resigned. Kate Forbes had less than a day.

At the age of 29, she became the first woman to deliver a Scottish budget, having to step in after Derek Mackay resigned as finance secretary.

Image copyright Getty Images Image caption Kate Forbes was the first woman to deliver the Scottish Budget

"I realised I didn't necessarily have a choice," she said. "And in the next seven hours, I had to wrap my head around every line of the budget and deliver the statement and answer questions.

"Who wouldn't be worried about delivering a budget with a few hours' notice? It was a case of tunnel vision, focus, and get ready to deliver."

The first-term MSP, at the time a junior minister, was then required to lead talks with opposition parties to ensure the budget was approved.

Some of those politicians praised Ms Forbes for stepping in to deliver the £34bn budget, but were critical of some of the content.

A speech to remember

Shy and nervous, with a bad stutter, George VI never expected to be King. The abdication of his brother Edward VIII to marry the American divorcee Wallis Simpson put him, somewhat reluctantly, on the throne.

Image copyright Getty Images Image caption George VI has been called the reluctant King

The King and Queen Elizabeth, later the Queen Mother, won enduring popularity with the British people when they stayed at Buckingham Palace throughout World War Two, despite the bombing of London.

And the King set a lasting example to any public speaker by not letting his speech impediment prevent him giving speeches across the empire - not least to rally the nation at the outbreak of war.

This has been celebrated in the successful British film, The King's Speech.