The Ambassadors Theatre Group host star-studded summer party at Kensington Palace

It was serendipitous timing for the Ambassador Theatre Group's summer party last night, as the UK briefly enjoys its long-promised (but looking to be all too brief) Indian summer. Sienna Miller co-hosted proceedings alongside Mark Cornell in aid of Sir Sam Mendes and his Theatre Artists Fund. Guests including Dominic West, George Osborne, Jonathan Newhouse, Sabrina Guinness, Geordie Greig and Sir Tom Stoppard gathered for vodka cocktails and roast beef canapés in the sunken garden at Kensington Palace, with many stopping to admire the recently unveiled Diana, Princess of Wales memorial statue. Eddie Redmayne enjoyed a night out with his wife Hannah Bagshaw, ahead of rehearsals for his next theatre project, Cabaret, which will be showing at the Kit Kat Theatre in the winter. Lord Dalmeny led an energetic auction with a surprise lot, 'a "sleeper" as it's known in the industry,' he explained, which caused the biggest stir of the evening. The prize? Lunch with Sienna Miller. The winner? Her handsome boyfriend, Archie Keswick, of course. The crowd became increasingly lively as the night wore on, encouraged by Gala Gordon, former Tatler cover star Jenna Coleman and her The Serpent co-star Fabien Frankel, who all hit the dance floor enthusiastically for Hugo Heathcote's DJ set. What a joy for parties to be back again.