The wedding of the prince and Kate Middleton in April will be covered by a number of counter-terrorism measures - including the elite soldiers who will work with police officers on the big day - amid fears that the occasion will be the perfect opportunity for an attack.
A senior security source said: "One of the biggest fears is that terrorists may one day try and launch a Mumbai-style attack on British streets and that could be on an iconic day like the royal wedding.
"If that happens then there is no substitute for combat experience and knowing how to deal quickly with those trying to cause harm to British people. That is a job for our police with some input from special forces."
The snipers will blend in with the crowds and watch vulnerable points along the wedding procession route from rooftops and unmarked cars and vans.
The security insider added to the Daily Mirror newspaper: "Officially this does not happen but very occasionally special forces operators and military specialists are needed on the ground. Since the 9/11 attacks there has been an increasing military presence among the police force both operationally and in planning for big events.
"They are a vital addition to the police-led operation to ensure as little risk as possible from a terror attack on the wedding day."
