The nest will be undisturbed until the birds fly away
A nesting bird looking for a place to bring up her young decided the safest option was with 24-hour security.
The blackbird made her nest on the back wheel of a police patrol vehicle in a compound at the Norfolk force headquarters in Wymondham.
The nest must be undisturbed until the fledgling birds have flown the nest or the force would risk breaking the law.
All wild birds, their nests and eggs are protected by law under the Wildlife and Countryside Act 1981.
Wildlife liaison officer Pc Garth Coupland said: "It's not the first time this has happened. Nesting birds should always be left undisturbed or you run the risk of the parent abandoning its young.
"Fortunately on this occasion the mum chose a vehicle that's not yet fit for the road anyway so no-one is losing out.
"Hopefully it will leave us with another satisfied customer - albeit a feathered one."