Typically armoured cable is used - deeply buried or firmly fixed above ground - and connected to an RCD in the property - however....
In the UK this work is notifiable to the local authority so that a safety inspection may be made (£) so it might be best to have it done by a qualified and certificated tradesman (££).
http://www.diydoctor.org.uk/projects/partp.htm
Peccavi, April 2010
