The famous music hall comedian, Fred Karno, attempted to turn the island into a pleasure garden and rebuilt the Thames hotel there. It is said that in doing so he ejected some Gypsies. Never ones to take kindly to such acts, they allegedly laid a curse on those that would come after them. Karno sold the hotel in 1926 and after a chequered history involving many financial collapses, the building was demolished in 1971 and never rebuilt. Gypsies were invited back to lay the curse. The houseboat residents, who set the island up as a houseboat community, eventually acquired the island.
For further information, please read Haunted Britain by Antony D. Hippisley Coxe.