Sub-zero marathon on Siberian frozen lake
British runners have been taking part in one of the world's most extreme marathons - in sub-zero conditions across frozen Siberia.
They were among less than 150 competitors in the marathon across the ice of the planet's largest and deepest fresh water lake.
Held during the Siberian winter, the Lake Baikal Ice marathon is like no other marathon on Earth.
Run between the shores of the vast lake on thin ice only 80cm thick, offerings to the spirit of the lake are mandatory for any entrant before the start.
It starts just after sunrise at 9am when the temperature is minus 12C but attracts a field of international runners many of whom live for extreme sports.
The best complete the race 50% slower than any ordinary marathon race because of the brutal running surface.
The clear air and flat terrain means runners can make out the distant finish line almost as soon as they begin - giving them nothing to focus on but how far they are from their goal.
British runner Alex Teddy, from Oxford, who completed the full distance, said: "This is my first ever marathon.
"I figured that marathon running was a bit boring, so decided to run on ice to add a bit of spice and adventure."
Local runner Sergei Kalashnikov won the race in a time of 3 hours and 7 minutes, hardly a world record time, but a huge achievement considering the conditions.