Surrendering Indian passport with no naturalization certificate

I have been an Indian citizen by birth, and have had only Indian passports till very recently. A few months back, I became aware that my father's birth in the UK meant I might have a claim to British citizenship. I tested this claim by applying for a British passport, which was subsequently issued. I now want to surrender my Indian passport, but surrender always seems to require a naturalization certificate to verify the date of acquisition of foreign nationality. I, of course, have no such certificate. Can anyone advise me on what to do in this situation? Should I write a letter with my application explaining my situation? Has anyone been in a similar situation?