Grayson Perry, whose work is on show at the exhibition in the RA’s Piccadilly home, dressed for the hot weather in a vivid frock as did other familiar faces including actress Laura Carmichael, Lila Moss and Lady Amelia Windsor.
Other partygoers basking in the sunshine included DJ Nick Grimshaw, who helped supply the music, and Bridgerton star Simone Ashley.
They were joined by singer Neneh Cherry and actors Hayley Atwell and David Oyelowo.
Last nights party was held on the hottest day of the year so far with a sweltering 28.2C recorded at Kew Gardens and more records are set to be broken as the week goes on.
Temperatures of 29C are expected today as music lovers flock to the Isle of Wight for its annual festival with Muse and Kasabian among the headliners.
Festival bosses have warned revellers to seek out the shade and take regular breaks and stay hydrated as temperatures continue to rise with Friday potentially hitting a sizzling 34C.
The warm weather is coming from Spain and Portugal where daytime temperatures have topped 40C in southern Spain.
Britain’s highest recorded June temperature is 35.6C - recorded in Southampton during the 1976 heatwave.
Before Wednesday, the hottest day this year was in mid-May when temperatures hit 27.5C at Heathrow.
Health chiefs have already issued a heat alert coming into place at midnight tonight (thurs) and lasting until midnight on Saturday.
Dr Agostinho Sousa, Head of Extreme Events and Health Protection at the UK Health Security Agency, said: “We want everyone to enjoy the hot weather safely when it arrives and be aware of good health advice for coping with warmer conditions.”
The weather is expected to break on Sunday with temperatures plummeting by as much as seven degrees C while rain is also expected to dampen down the heatwave.