Please post up a GSV link to the location where your friend parked.
If the PCN has been lost then how did you manage to get the PCN details on the Hackney website?
Please confirm your friend is not a Hackney resident and doesn't have a Hackney companion e-badge?
The on-street PCN was served on the 15th November. So the 14 day period to pay at the discount rate expires on Tuesday the 28th November. If informal representations (challenge) are submitted within the 14 day discount window then Hackney would normally reoffer the discount if they refuse the informal reps. So you have nothing to lose by having a go. Just get it done by Tuesday.
In Hackney a BB holder cannot park in resident permit only bay. A P&D or a shared use bay bay would have been OK.
I would try mitigation if the location and/or signs don't help. Terribly sorry, I misunderstood the BB rules for resident permit bays, in my borough BB parking in residents' bays is allowed, I made a mistake, it won't happen again, there was no intent to evade a parking charge and so on.
Also it seems that Hackney are planning to change their rules so that BB holders can park in permit bays. They're having a consultation about it. So suggest that it wouldn't be in the interests of justice to enforce a PCN when they're about to change the rules and eliminate the alleged contravention.
Please see
top of this page.
And also see here.