No cover in London

After many years of comprehensive cover, insurance companies are telling me they can only offer third party cover because I live in London where the risk of theft is high. Is this widespread in the capital? It seems that while the mayor, Sadiq Khan, and the police are urging us to do more stop our bikes being stolen, insurance firms are deciding they no longer wish to help once a theft has taken place.

Giles Elgood, Islington