In message , Steve Walker
writes

It's probably not that great a risk in a domestic setting, but in
industrial and commercial premises, they go to great lengths to ensure
that there are no dead-legs in the hot plumbing as they can be a
breeding ground for legionella.

That is a cheerful thought, thank you :-)

Having said that, the pipe I cut was feeding a tap that has not been
used for at least 16 years, so nothing has changed except the tap being
replaced by a stop end.
--
Graeme