Conservative Brexit backer Jacob Rees-Mogg was just one of the MPs IBTimes UK spotted as they left The Ritz on Wednesday night (24 November).
The North East Somerset MP was among more than 100 guests at an exclusive party for Nigel Farage.
The Mayfair bash was reportedly put on by insurance tycoon and Ukip donor Arron Banks as well as the Barclay brothers, who own the hotel.
"On the night of 23 June, for those of us who had thought it and felt it and believed it and prayed for it, was that not just the most amazing evening?" Farage told the guests, according to Sky News.
"I still remember coming here for breakfast the next morning at 7 o'clock to celebrate with champagne and kippers. 2016, when people look back in 100 years, 200 years, will stand out as one of those great historic year. It's the year of the big political revolution."
He also predicted a "seismic shock" at the next general election if Theresa May fails to deliver on her "Brexit means Brexit" promise.
The interim Ukip leader was pictured holding a stacked tray of Ferrero Rocher, a reference to the chocolate being the "Ambassador's choice" after President-elect Donald Trump backed Farage as the UK's top diplomat to the US.
Some of Farage's most loyal allies were also in attendance, including Ukip London AM Peter Whittle, Tim Aker MEP and the party's communications chief Gawain Towler.
Ukip's next leader will be elected on 28 November. Former deputy leader Paul Nuttall, former deputy chair Suzanne Evans and former parliamentary candidate John Rees-Evans are competing for the post.
The Times, meanwhile, has reported that Farage plans to move to the US with his wife, Kirsten.
This article has been amended to reflect the fact that although Iain Duncan Smith was outside The Ritz he was in fact walking to the nearby Carlton Club and did not attend the Farage party.