http://www.mondaq.com/article.asp?articleid=41212&searchresults=1
Sally Ramage
"Subject to statutory exceptions to the contrary, a person whether English or not, who commits crime abroad is not indictable here. In construing Acts of Parliament there is a well-established presumption that, in the absence of clear and specific words to the contrary, an "offence-creating section" of an Act is not intended to make conduct taking place outside the territorial jurisdiction of the Crown an offence triable in England. The presumption against a Parliamentary intention to make acts done by foreigner’s abroad offences triable in English criminal courts is even stronger". [Free signup required]