
Three men and two women of the King's Troop, Royal Horse Artillery, were sacked after traces of the class-A drug were found during a routine test.
Their 130-strong unit, which is part of the Household Troops, normally performs at royal occasions and state visits.
The soldiers' fall from grace came just months after they fired a salvo as part of a welcoming ceremony for French president Nicholas Sarkozy on a state visit t Britain.
A Ministry of Defence spokesman said: "Drug misuse in the Armed Forces will not be tolerated." He pointed out that less than 1 per cent of Army members test positive for drug use, while the figure in civilian jobs lies around 7 per cent.