A sixth person has been charged with being part of a suspected Russian spy ring operating in the UK.
Tihomir Ivanov Ivanchev, a 38-year-old Bulgarian national, from Acton, west London, was arrested on 7 February and will appear in court on Wednesday.
He is accused of "conspiring to collect information intended to be directly or indirectly useful to an enemy".
Five other Bulgarian nationals are due to go on trial in October after being accused of similar offences.