It is believed ravens have been living in the Tower of London since at least the time of King Charles II and legend maintains that if they ever leave the tower and the monarchy will crumble — although this may all be Victorian fiction. Allegedly too when Charles II received complaints that the ravens were interfering with the work of the Royal Observatory, he ordered the re-siting of the Observatory to Greenwich rather than remove the ravens.
About the only restraint on the ravens is that they have the flight feathers on one wing clipped to prevent them flying off (they can however fly short distances to perch) and, as I recall, they are caged overnight. Otherwise the ravens are free to roam the tower grounds and do much as they please.
And do the ravens have a good life! As Wikipedia notes, quoting Boria Sax:
The ravens are now treated almost like royalty. Like the Royals, the ravens live in a palace and are waited on by servants. They are kept at public expense, but in return they must show themselves to the public in settings of great splendour. So long as they abide by certain basic rules, neither Royals nor ravens have to do anything extraordinary. If the power in question is political and diplomatic, the Royals now have hardly more than the ravens. But the word "power" here can also mean the aura of glamour and mystery which at times envelops both ravens and monarchs.This is rather exemplified by another brilliant quite in the BBC News piece from Chris Scaife, the Yeoman Warden Ravenmaster:
"Raven Jubilee is doing very well and has now been trained to come out of his cage and meet all the visitors ... But it takes years for the birds to really get to know members of the raven team and for us to get to know them and their idiosyncratic ways."And that's despite they're each fed around 8oz of meat a day plus fruit, cheese, eggs and bird biscuit.
He added: "They are the most pampered birds in the country — and one of the most intelligent. They gang up on small children with crisps at the tower — but they don't like cheese and onion — so they'll open the packet and dip the crisps in water to get rid of the taste."
What brilliant birds!