The Queen is covered by what is known as sovereign immunity in the UK. It means that the sovereign cannot commit a legal wrong and is immune from civil or criminal proceedings. ... The law also states that no arrests can be made in the monarch's presence, or within the surroundings of a royal palace
Nowadays, the Queen in her personal capacity is considered for legal purposes the Crown as Sovereign and as such immune to prosecution. ... That's the same as other heads of state, at least during their terms of office - and the Queen holds her office for life