Stringer, of Essex Road, Islington, was arrested on January 26, while Johnson, of Tilney Gardens, and Ndayizeie were arrested on February 10.
Detective Constable Will Wigzell, from the Met’s Flying Squad, said: “These robberies have a lasting impact on businesses, their staff and the wider community, affecting livelihoods as well as causing significant emotional and financial harm through the threats, violence and intimidation involved.
“This organised crime group carried out a series of brazen smash-and-grab robberies across some of London’s busiest shopping districts.
“They carefully planned their offences, using stolen vehicles and mopeds in an attempt to evade detection, but thanks to the determination and expertise of Flying Squad detectives, they were identified and brought to justice.
“These sentences mark a significant milestone in what has been a detailed and determined investigation.
“I hope they demonstrate our commitment to tackling smash-and-grab robberies in London by pursuing those involved, wherever they are.”