Here's the sign at the bus stop : -
https://maps.app.goo.gl/6FoCrw4ae7qhLLT5AI must say, I'm surprised you say you know nothing about this rule, as most bus stops in London seem to be subject to this No Stopping restriction. It is also used throughout the UK.
You also say you gave your friend two more lifts in May. Can you remember on what dates these were, because there is a 28 day limit on service of a PCN in the legislation they are useing to enforce these bus stops.
It's difficult to suggest a strong appeal case, their video shows you stopping for 54 seconds, so the contravention is made out. Just remember for the future, that you can stop to board or alight passengers on yellow lines, provided there is no loading restriction there.
As this is Havering, there may be a technical appeal based on their mismanagement of the enforcement process, so wait a bit until others more expert on this than me contribute, but don't miss the PCN deadline for paying or submitting representations.