Ice in the Serpentine lake in Hyde Park, London, forced swimmers to abandon an open-air race on Christmas Day.
About 40 people had hoped to take part in a 100-metre swim there, but the ice forced organisers to cancel the event for the first time in nearly 30 years.
However, the ABC reports dozens managed a quick dip in a small area where they had smashed the ice.
Serpentine Swimming Club secretary Brian Thomas, said the last time it was frozen over on Christmas morning was 1981.
The event was first held in 1864.
December is expected to be Britain's coldest since records began in 1910.