The letter to Richard Haig at the end of the film is addressed to 170 Trinity Lane, Cambridge CB2 TTB.
There are barely a handful of buildings on Trinity Lane to come close to 170 (most aren't numbered anyway, just college names). Also, the postcode looks like it was incorrectly transcribed by the researcher - Trinity Lane postcodes are CB2 1T* See more
It's important you understand, it's not you, it's me. What we have is so special. I love you more than I can say, but I'm sorry, truly, because, I fucked up.
[we see that he is talking to a young boy
Look, I owe you an explanation, but honestly, I don't know where to begin.