Kate, who is currently pregnant with her third child, appeared with the smallest hint of a baby bump on show through her sky blue floor-length Jenny Packham gown embellished with jewels just two months after Kensington Palace confirmed the news that a new royal baby is on the way.

On October 17, Kensington Palace confirmed on Twitter that the due date is in April 2018.

Tonight, the Duchess was joined on the red carpet by husband Prince William for the variety performance, and wore sparkly silver stiletto heels which peeped from below her floor length gown.

She also held a small silver box clutch, and wore her hair in tight chocolate brown curls which fell around her face.

The royal couple arrived an hour later than scheduled for the star-studded evening gala at the London Palladium but were greeted by eager fans and a bunch of flowers for the four-month pregnant Kate.

Kensington Palace tweeted: “The Duke and Duchess of Cambridge are tonight attending the @RoyalVariety Performance.

“The Royal Variety Performance takes place every year and is in aid of the @RoyalVariety Charity, of which The Queen is Patron.

“The money raised from the show helps hundreds of entertainers throughout the UK, who need help and assistance.”

Tonight’s Royal Variety performance marks a return to the London Palladium Theatre after the event moved elsewhere for the last two years.

The Palladium has been home to the Royal Variety Performance more than any other venue, hosting the gala 40 times over the decades.

And this year the event is being hosted by comedian Miranda Hart, with guests including the cast of 42nd Street, Paloma Faith, Michael Ball and Seal.

There was a false start to the event as the curtain did not go up for the first act - a glittering tap dance bonanza from the cast of the 42nd Street stage show.

Host Miranda Hart jokingly teased the audience about whether they spotted if anything had gone wrong before reintroducing the act.

Kate, 35, was left in fits of giggles when her husband was forced into a spot of audience participation with the lights shining on him.

Wiliam, 35, enthusiastically took part in a comedy skit with Hart, obligingly shouting her catch-phrase "such fun" on request.

Hart, who said compelling the future King to participate was on her to-do list for her Royal Variety duties, said she later hoped to see him galloping - another one of her trademarks - and "knighting me with a lightsaber".

Singer James Blunt, who was due to the perform, was a last minute withdrawal after the delayed start meant he would not make an later concert appearance, according to a theatre spokesman.

A Kensington Palace spokesman said the royal couple had been "delayed" but were in time for the start of the performance.

The performance will be shown on ITV in December.

The delayed appearance comes after Scotland Yard urged anyone on Oxford Street to "go into a building" after gunshots were reported at about 4.38pm. One woman was injured as she left the train station.

Police say they initially responded "as if the incident is terrorist-related" but have since said they had not yet found any suspects or any evidence of shots being fired at the station in Oxford Street - which has since reopened.

The incident has now been stood down and it is thought the "shots" could have been an "electrical fault".

Oxford Circus Tube and Bond Street stations have reopened, most cordons have been removed and the area has returned to normal.

A traditional pre-show line-up, in which some of the performers proudly get to meet the royal party, had to be dropped following the incident.

Police are now investigating what caused panic among thousands of rush-hour commuters and Black Friday shoppers in the heart of central London.