Thursday was also the hottest day of the year so far, beating the previous high of 26.7C recorded in Wisley, Surrey earlier this week.
Temperatures in London soared above several European cities, including Athens and Rome.
The capital was also hotter than Cairo (27C), Marrakesh (27C) and Los Angeles (21C).
While not expected to hit the same sort of peaks as Thursday, temperatures are on course to remain high for many on Friday.
However, conditions are forecast to return to closer to seasonal averages across the Bank Holiday weekend.
Temperatures are expected to reach the low twenties in the south of England, with highs only reaching the mid-teens further north and in Scotland.
