British musician CHRIS MARTIN has been secretly helping out a London charity by fixing their water pipes.

The Coldplay star - married to Hollywood actress Gwyneth Paltrow - has put his technical skills to the test and brought festive cheer to staff at homeless charity Crisis.

A source tells British newspaper the Daily Express, "Chris has been doing their plumbing for them."He does this every year, for free, on the hush, hush. Apparently he's quite a dab hand with it all." A Crisis spokesman says, "We have 7,000 volunteers helping at Christmas. There are celebrities among them but we can't name those who wish to remain anonymous."