Here's what's so cool about this: It's not necessarily even illegal. In England squatting is not against the law as long as there is no forced entry and no damage is caused. Laws governing adverse possession could eventually give these squatters legal title to the property if the Duke of Westminster doesn't do anything to stop it. Under British law, they'd have to occupy the property for more than a decade and meet some other terms and conditions. Given that the two properties are valued at something like $40 million, that seems unlikely.
A spokesman for the Duke of Westminster's Grosvenor Estate told one newspaper that the two buildings are currently leased by a separate company, and that that company would be responsible for any attempts at eviction.
It's hard not be happy for these young people. They've taken up shelter in beautiful homes that were sitting by unoccupied, and they don't seem to be damaging anything.