In message , David
Cantrell writes

The *really* important question is whether you get let off the
congestion charge when the filth divert you off the free roads.

According to the CC FAQ:

If you are diverted into the charging zone by an official diversion or
by a police officer, you do not have to pay a Congestion Charge.

You must ensure that you leave the Charging Zone as directed by the
diversion, or, if no signage is provided, at the first available
opportunity.

If you enter the Charging Zone at any other time during the same day, or
deviate from the diversion, you will need to pay the Congestion Charge.

Transport for London (TfL) will endeavour to ensure that all vehicles
subject to a diversion will not receive a Penalty Charge Notice (PCN).

In the event that a PCN is received, TfL will consider any
representation against a PCN issued in such circumstances. Full details
of the diversion should be included in the representation.

--
Paul Terry