In message
,
Mizter T writes

For a while I've thought it somewhat ridiculous that there
doesn't appear to be any information on the web about when the routine
maintenance closures of the Rotherhithe and Blackwall tunnels take
place - the whole issue seems shrouded in mystery!

www.blackwalltunnel.com
and
www.rotherhithetunnel.com
are unofficial but very helpful.
--
Paul Terry