The four were seized on Sunday as they were shopping in Rabat's largest supermarket, police said, adding that police mounted a sizeable operation because the suspects were "specialists in martial arts and the use of weapons".
British police have charged seven people in connection with the February 22 robbery on a Securitas depot in southern England.
The arrests came after a three-month investigation by Moroccan police in cooperation with their British counterparts, the Moroccan statement added.
Moroccan police did not say if or when the four arrested suspects would be handed over to Britain. The statement did not name those arrested.
After the arrest, police searched the Rabat residence of the four men. The men were wanted by Interpol and Scotland Yard was involved in their capture, Moroccan police sources said.
The February 22 loot of 53,116,760 pounds was more than double the previous record amount stolen in a British cash robbery - the December 2004 heist at the Northern Bank headquarters in Belfast which netted 26.5 million pounds.
The hold-up also dwarfed other notorious raids like the 1963 "Great Train Robbery" by Ronnie Biggs, who made off with some 2.6 million pounds or the the equivalent of 33.45 million pounds in today's money.