Barschak climbed over a wall and talked his way into the party

After a Metropolitan Police internal inquiry, a sergeant and two constables will be given "words of advice".

An inspector and two constables will get further training in operational planning and control room systems.

Comedian Aaron Barschak breached security at William's 21st last June, dressed as Osama bin Laden.

What happened was a combination of systematic, procedural and personal errors Deputy Assistant Commissioner Steve Roberts

The self-styled comedy terrorist was not arrested until some time after he had interrupted Prince William while he was giving a speech to guests in the dining room.

A chief inspector on duty that night has already been transferred to a non-operational role.

The Met says security at the castle has been tightened since Barschak's stunt.

Deputy Assistant Commissioner Steve Roberts, director of professional standards, said: "It is clear that what happened on the night was a combination of systematic, procedural and personal errors compounded by insufficient training.

"Whilst we have taken on board the gravity of this breach of security, these sanctions are commensurate with the individual parts each officer played in this incident."

Speaking shortly after the incident, Home Secretary David Blunkett said: "Mr Barschak's actions have exposed an appalling failure in the security at Windsor Castle which simply should not have happened."