Firefighters went on strike for an hour last night part way through tackling a large woodchip and log fire behind a pub.
Contingency crews took over between 11pm and midnight behind the Star in Kingston Road, Malden Rushett.
A London Fire Brigade spokeswoman said four fire engines were called to the fire at 6.50pm and firefighters were still there this morning.
She said a pile of woodchips, measuring 25 metres by 15 metres, was 30 per cent alight and 10 per cent of the wooded area and logs were alight.
A witness to the fire said: "There was a break in London and Surrey dealing with it because of industrial action.
"On-site security noticed how good the first crew was and how not so good the middle crew was."
Leatherhead firefighter James Oatley, who helped to fight the fire, said the blaze initially created a lot of smoke.
Mr Oatley said: "There was no life risk and it was in the middle of nowhere. We still chose to leave before industrial action happened."
The Fire Brigades Union (FBU) is staging daily strikes, between noon and 2pm as well as 11pm and midnight, in an ongoing row over pensions.
The string of strikes started on Saturday August 9 and tomorrow is the last day of the industrial action.