Thanks but as I mentioned I have switched this feature on. If I hadn't switched this on I would have got the error message:
Msg 15281, Level 16, State 1, Procedure xp_cmdshell, Line 1
SQL Server blocked access to procedure 'sys.xp_cmdshell' .....
But I don't get an error message: Regardless of the command entered I get
output
----------
NULL
Francis