Free Traffic Legal Advice

Hm. Signs are the normal size for this sort of thing, the same size as the traditional 'No Entry' sign. Would you have gone past one of those ? Very unwise to rely on satnavs in London as these LTN zones are all over London and most satnavs are out-of-date.

Two things come to mind, (1) the signs are not illuminated, and the video shows you going from light into a much darker part of the street, so your eyes would not have had time to adjust, and without them illuminated, much more likely to be missed. (2) Against (1), is the presence of an advance warning sign: -
https://maps.app.goo.gl/6drnhYHhAeit6EZu9

So difficult to see anything to refute the contravention itself, but that doesn't mean it's game-over, because errors and omissions have been found with several London councils management of the enforcement process. These errrors can win an appeal on their own, but you have to take the council to London Tribunals for a result. Hopefully the experts will soon be on to tell you if Hackney are mismangeing the process.

I don't think there are many successful appeals for this bus gate and I'm not aware of issues with Hackney's PCNs.

All anyone needs to do is know the PCN number and your numberplate. If you read the top of page 2 (You are entitlted to...) it gives the website to use. You have kindly provided the rest.