Normally buying a Glasto ticket means waiting for a buying slot on one of a handful of dedicated computers, aka servers, that See make available for this task, and to access them you go through the normal https://glastonbury.seetickets link.
These servers, as we know, are heavily overloaded with handling these ticket transactions, so most of us are held at a waiting screen for our opportunity to transact with them.
But it appears that See also have some other ticket servers, either held in reserve in case one of the main ones fails, or indeed kept back from the Glasto ticket sale to service any other ticketing tasks for other events, as they wouldn't want to degrade the performance for these events just because the Glasto sale is on at the same time.
However, these other servers *can* also sell Glasto tickets, if asked nicely, as they are connected to the same back-end See tickets system.
So there is a hack you can do to your own computer's files to make it approach one of these ticking-over servers *as if it were* a dedicated Glasto ticket server, and it appears that under these conditions these spare servers will in fact then process the ticket application successfully. They are far less overwhelmed with requests for tickets, since they are not officially available to Glasto ticket buyers, so they are far easier to get an open ticket-buying slot on.
So this 'hosts file' hack directs your request for a Glasto ticket (deposit) to one of these servers instead - and it works!
(Not that I used it fwiw)