The message from Andy Wade contains these words:
Unlikely in a double socket in a shed.
I worked for a firm who had a Portacabin delivered one day. Rather than wire it in properly to the factory's supply, 'cos it was a Saturday and the sparks wasn't available then boss made up an extension lead with a plug at each end - one end went into a handy socket in the factory, the other end went into a handy socket in the Portacabin.