OK, so whenever I see a thread on the lines of "I didn't see any signs at all" (or in a similar vein), I go to look at what Google Street View shows. Maybe you've already done this, but anyway, here's what I found.
For the Blackwall tunnel, the one you used, on GSV on the southbound approach there are these signs, which no doubt you are not familiar with: -
Find local businesses, view maps and get driving directions in Google Maps.
and
Find local businesses, view maps and get driving directions in Google Maps.
after this sign, GSV reverts to 2024, so if there are signs, I can't view them.
Note the "C" on a red background. That is now the standard sign for indicating a road user charge, athough that is all it tells you, not how to make payment.
There is also this sign telling you a payment is required:-
Find local businesses, view maps and get driving directions in Google Maps.
Going northbound, GSV seems similar, with the signs here: -
Find local businesses, view maps and get driving directions in Google Maps.
and nothing on this sign after the one above:-
Find local businesses, view maps and get driving directions in Google Maps.
then the "C" appears, but so inoccuous and small one could be forgiven for not noticing it.
https://maps.app.goo.gl/6iRdFsekvNqCWQQv5and again
https://maps.app.goo.gl/NCBSC4NEF3WBy1MJ6then this
https://maps.app.goo.gl/xCUSmyuHJHNA2Z4x8and again the "C" sign
https://maps.app.goo.gl/m8D14284skk1ncpV6the a sign gantry specifically to show the toll signs
https://maps.app.goo.gl/DLvJKfP9prBiHAPA6and finally the original tunnel entrance of 1987 !
https://maps.app.goo.gl/DLvJKfP9prBiHAPA6As you will have no doubt already gathered, there are two tunnels, the new Silvertown tunnel, and the older Blackwall tunnel which used to be free-of-charge until the Silvertown tunnel opened using financing that demanded it be tolled. So just like the new Mersey Gateway Bridge, built up-stream of the existing bridge at Runcorn, which again was financed on the basis of a toll for use, the old and previously free bridge was also tolled, to prevent loss of revenue. So just as on the Mersey in London, when the new Sivertown tunnel opened with tolls, the Blackwall tunnel became tolled to ensure there was no loss of revenue.
The tolls on the new tunnels commenced on 7th April 2025 when the Silvertown tunnel opened. For quite a few weeks, enforcement was undertaken by sending our warnings to first-time non-payers, but that has now ceased. Biggest problem we see on this forum is people using satnavs, and getting caught out by new restrictions especially in London. As you can see, it's not quite a year since those new tolls came in.
Assuming the signs I have shown above have not been improved, for me it is totally inadequate for a stranger to London, but so far, I don't think anybody has challenged the signage at London Tribunals and won on the basis of inadequate signage. Adequacy is the standard within Regulation 18 of The Local Authorities’ Traffic Orders (Procedure) (England and Wales) Regulations 1996
https://www.legislation.gov.uk/uksi/1996/2489/regulation/18So it might be worthwhile submitting representations that you are a total stranger to London and saw nothing on Google or your satnave that indicated the need to pay a toll on the Blackwall tunnel. Don't expect them to roll over and cancel the PCNs. Like London councils, TfL are as ruthless, venal, and rapacious as they are. Of course you have the absolute right in law to take them to London Tribunals, but would have to risk the full PCN penalties.