Not to break the joke or smth, but there's a video on YouTube (by ‘Strange Man’) that shows evidence of Nigel having schizophrenia and Gavin was a person he invented/imagined when he was still in London (if I remember correctly)
Yeah I watched the same video. In the letter it's hinted that Gavin is Nigel and vice-versa, and Nigel made up Gavin due to the loss of his father. It's also hinted at when the writer of the letter beat up a guy for making fun of Nigel.
