"A few minutes" has been two and a half hours so far.
Most people in the UK don't have to fill in tax forms, but I do because I receive earnings from consultancy and book royalties. It's not hard, it's just tedious to sort out the paperwork in advance then perplexing trying to figure out where in the forms the data should go. This is why I was putting it off.
The deadline for self-assessment is January. My desire not to have to spend an hour wrestling with a form is in competition with HMRC's lax attitude to fixing "technical difficulties" to decide why I'll be fined for a late submission.