Codebreaker found in bag attended US security conference before death (2012)

He might have been a pre-Snowden that didn't escape:

Williams was unhappy with his work environment at MI6 and felt he didn't fit in with his colleagues. During the inquest, testimony revealed that the coder had conducted unauthorised searches of an MI6 database

also: http://www.wired.com/threatlevel/2010/08/codebreaker-death/

Killing someone and locking them up in a duffel bag in a hotel bathroom doesn't seem British governments style. Before claiming the victim was another Snowden/whistleblower, you might want to read this excerpt from the article:

"The source indicated that Williams' work to disrupt the Russian mafia could have put him at risk".

"Some of these powerful criminal networks have links with, and employ, former KGB agents who can track down people like Williams," the source said.

Wait, so what exactly is the British government style of killing people?

If you assume the British government chooses to murder people, it also perfectly reasonable to assume that it does it using someone else style to cover its crime e.g. russian mafia style.

The style of a security agency generally would be to make it look like either an accidental death (car crash) or a natural death (exotic virus), so as not to attract the attention of the police or the press. The mafia style, on the other hand, would be to make it clear that he had been executed, so as to send a threatening message to the appropriate circles.

he could be potential leak, they could do it this way so rest knows how leak will end for them.

Easy and effective.