dirmngr had selected sks.dumain.co.uk (85.119.82.209) as its host for
hkps.pool.sks-keyservers.net. Connections to that host were failing because its
X.509 certificate was expired. However, dirmngr would try that host repeatedly
(and would repeatedly fail).

It seems like such a host should be automatically marked as dead so that at
least subsequent tries will succeed (perhaps the next host should be
automatically re-tried as well).