asked Her Majesty's Government:

What arrangements exist for ensuring that passports of persons who have changed their names are cancelled pending the issue of a new passport.[HL1412]

There is no legal obligation for a person changing their name to notify the Identity and Passport Service (IPS) of the change until they apply for a passport. However, a person wishing to obtain a British passport in a new name must submit evidence of the change of name and surrender any existing passport held. On the issue of the passport in the new name, the previous passport record is cancelled on the IPS's database. In the event that the passport in the original name is declared to be lost, the details are notified to the Immigration Service, Interpol and others via the Identity and Passport Service's database of lost, stolen and recovered passports.