Prior to 1932, British subjects who held a European title could apply for a licence to use and be recognised by that title. Some were granted permission but many were refused for various reasons and there were no hard and fast rules as to who would be successful and who would be disappointed. 

In 1893 Queen Victoria decreed:

In future the rule is to be that all applications for the Royal licence to use Foreign titles in this country are to be refused. There may be special cases of an exceptional kind in which the Queen may be properly advised to relax the rule, but they will probably be of very rare occurrence and can be dealt with as they arise.

Subsequent monarchs confirmed that this was still the case: Edward VII in 1901 and George V in 1911.

With the outbreak of the First World War there was a general rise in anti-German feeling which famously led the Royal Family to change their German surname of Saxe-Coburg and Gotha to Windsor. At the same time, the Home Office made the decision that any German or Austrian citizen who held a title and applied for British naturalisation should discontinue the use of their titles as part of the application. In 1922, this ruling was later extended to titles from other countries.

However, there was no law and no real structure and the monarch could still make an exception if he wished. It was therefore decided to settle the matter once and for all and with the issuing of a Royal Warrant in 1932, the right of use of foreign titles by British subjects was abolished and no further applications for Royal Licences could be submitted for consideration. 

Any British citizen who currently holds a foreign title cannot therefore use that title in the United Kingdom or the Commonwealth. Nor can they compel any person, company or government office to include that title in any record they might hold, and they cannot insist on being referred to by that title.