As much as I loath some the methods deployed by the tabloid press, the gentleman in question needs to secure the services of a publicity agent such as Max Clifford.
Before you shoot me, this has been successfully utilised on previous occassions.
Person accussed secures the services of said like person, said like publicity agent evaluates the case, and in return for a complete expose after legal action is completed, said publicity agent secures the services of a top notch barrister.
I fully expect that faced with a legal team who actually know what's what, I expect that the arrogant and faceless pen pushers who run the UK defence forces would withdraw any action immediately.
Good luck to the gentleman involved.