I'm sure it's little consolation, but London Underground are contractually bound to fully refund the cost of a single cash ticket (£4) for any journey which is delayed by 15 minutes or more.

Here is a link to the website:

https://www.tfl.gov.uk/tfl/tickets/r...nd/default.asp

When commuting on the Northern Line, I used this ALL THE TIME and collected a couple hundred quid in vouchers each year. Every time the Tube is shut for 'engineering work', you can submit if you have to take an alternative route.