Apparently not, in the case of Daniel James, who, for some reason is facing charges under the Official Secrets Act and Misconduct in Public Office, in a civil court, rather than facing a military court martial, as a serving British soldier in Afghanistan.
According to the media, Daniel James is apparently
"the first person for more than 20 years to be tried for spying"
and this is supposedly
"Britain’s first spy trial since the Cold War"
However, as Michael John Smith points out, there have been 3 convictions under the Official Secrets Act since "the end of the Cold War": - his own in 1993 , Rafael Juan Bravo in 2001, and Ian Parr in 2002.
There was also the Katharine Gun case where charges were dropped in 2004.
Michael John Smith also contends that Daniel James is being held at Wandsworth prison, rather than Woodhill prison, as reported.