I've sent a response to a demand for payment of debt by recorded delivery. The Royal Mail tracker indicates that the letter was delivered and signed for, although the name given and the signature are unrecognizable to me (the name isn't a name I would've expected given the people demanding the debt be paid). I've double-checked and the letter was definitely sent to the correct address, according to Royal Mail.
So, could the person demanding the debt claim, in court, that they had not received the response because someone with a different name signed for the letter? Do you actually need it to be signed for by a recognized person?