The suspect was arrested on Tuesday in south London and is being questioning about the Securitas depot heist four months ago in Tonbridge, southeast England, in which 53 million pounds ($96.94 million) was taken.
Kent Police have so far charged five men and two women in connection with the raid, which happened in the early hours of February 22 after the depot's manager, his wife and son were kidnapped.
The seven are due to appear at the Central Criminal Court in London on July 10 for a plea and directions hearing.
Meanwhile, a Kent Police spokeswoman said three men arrested at a shopping mall in the Moroccan capital Rabat with 26-year-old cage fighter Lee Murray, from south London, were not being sought in connection with the robbery.
Instead, they were arrested for trying to stop Moroccan police arresting Murray.
Britain has no formal extradition treaty with Morocco and will have to make a special, one-off request.
The last individual extradited from the north African country to Britain was in 1995 and police expect the process to last months.