The US would be happy to volunteer a few if it's a question of manpower. Britain would probably commit their own just to avoid that kind of situation.

It just doesn't sound like a good use of the officers' time.

They've had the guy detained without charge for 500-odd days. Facing some international criticism and generally looking like hypocrites whenever they want to criticize some other country for having political prisoners. The case has been through their Supreme Court and now there's yet another country involved in this international incident.

When I was in London last year there were helicopters circling continuously in some places. If Assange gives them the slip somehow, it's not going to be because the local police preferred to prioritize something else that day.