Sienna Miller’s secret dinner at King’s hideaway as she weighs up key royal charity role… Hope she changed out of her amazing outfit from the night before!

Sienna Miller’s secret dinner at King’s hideout as she ponders the most important role in the royal charity… I hope she’s changed out of her amazing outfit from the night before!

Sienna Miller had a secret dinner with the King and a VIP tour of Dumfries House in Scotland.

The Hollywood actress joined Cabinet ministers, including Chancellor Jeremy Hunt and members of the Privy Council, to help the King celebrate 15 years of restoration of the Ayrshire mansion he saved for the nation.

Mrs Miller, 41, who revealed her pregnancy bump in a striking outfit at the Vogue World party last week, was invited to stay overnight at the historic £45million home.

It is not known whether the actress’ boyfriend, Oli Green, 26, was invited. The actor will appear in the sixth season of The Crown as he plays law student Rupert Finch – an ex-boyfriend of the Princess of Wales and Prince William’s love rival at St Andrews University.

An insider said Ms Miller was one of a handful of celebrities considering becoming an ambassador for the King’s Charitable Foundation, which has its headquarters at Dumfries House.

Her visit on Friday was to help her decide whether to accept.

Sienna Miller had a secret dinner with the King and a VIP tour of Dumfries House in Scotland

The Hollywood actress joined Cabinet ministers, including Chancellor Jeremy Hunt and members of the Privy Council, to help the King (pictured) celebrate 15 years of restoration of the Ayrshire mansion he built for the nation had saved.

The Hollywood actress joined Cabinet ministers, including Chancellor Jeremy Hunt and members of the Privy Council, to help the King (pictured) celebrate 15 years of restoration of the Ayrshire mansion he built for the nation had saved.

Earlier this year, the Layer Cake actress attended a celebrity event for the Prince’s Trust, the King’s other long-running charity, alongside Rita Ora and Kate Moss.

But this would be the first time she has agreed to become an ambassador for the Prince’s Foundation, which gives young people the opportunity to develop skills with projects ranging from the hospitality industry to the textile industry.

However, the Foundation has come under fire in recent years. Michael Fawcett, a longtime aide to the king, was forced to step down from his role as CEO of the charity following a scandal involving millions of pounds in donations from foreign tycoons.

Two staff members were questioned by police after The Mail on Sunday revealed documents that appeared to have offered help to wealthy foreign magnates to obtain honors – including a knighthood – in return for donations.

An insider said Ms Miller was one of a handful of celebrities considering becoming an ambassador for the King's Charitable Foundation, which has its headquarters at Dumfries House.

An insider said Ms Miller was one of a handful of celebrities considering becoming an ambassador for the King’s Charitable Foundation, which has its headquarters at Dumfries House.

But the Metropolitan Police announced last month that they had completed their investigation and would not lay charges. An insider said there was a new push to sign celebrity ambassadors to help rehabilitate the charity’s image.

The source said: ‘There is a new sense of optimism in the charity.

“So on Friday there were a number of celebrities, including Sienna Miller, as well as many prominent politicians. But a private dinner celebrating a house open to the public seems strange if you ask me.”

Before the dinner, the King held a reception to mark the 15th anniversary of the opening of Dumfries House and estate to the public.

At 5.30pm he arranged a meeting with the Privy Council, attended by Penny Mordaunt, Jeremy Hunt and Grant Shapps.