The Party Wall Act 1996 introduced procedures which allows for and protects the rights of owners joined by a party wall.
The Act is not administered by any enforcement agency, but it places responsibility under law on the owners who may be party to the proposed works. If the Act is not followed, any court proceedings will take the provisions of the Act into account in additions insurers may well take non compliance into account.
For more information:
http://www.planningportal.gov.uk/uploads/br/BR_partywall_explain_booklet.pdf