Free Traffic Legal Advice

If he wins overall, all monies paid are recoverable, including bailiff's fees...may take some time but all must come back to him.
Pay now and claim back later is valid at this stage, if only to prevent further escalation of costs or enforcement action such as cars being clamped.

More to the point is what bruvver is going to achieve.
He has to provide a truthful statement that he did not receive one of the Notices that the procedure calls for.
Can he actually truthfully say that or is it more a case of he ignored the post that was being delivered. Does he know himself? (Don't answer these questions but be aware it is a criminal offence to lie on that statement)
He also has to provide an Out of Time request...basically a request for the statement to be accepted late and providing a good excuse.
Even the best of reasons can be objected to by the Authority, who normally do. An objection often finds the request denied.
Which means a request to a District Judge to decide... that s over 100 notes on a decision on papers or over 250 for a hearing... costs not normally recoverable.
Only when that lot is done can the PCN itself be appealed, at the moment it is about process not the rights or wrongs of the PCN.
It is about where the process went wrong and whether brother was blameless.

Absolutely. What are his options? Paying the £279 fine when he's paid the price he was asked is crazy.

The case history you showed says he never paid the charge at all?

Bailiffs cannot execute your brother's warrant at your address it is not where he lives. Paragraph 14(6) of Schedule 12 of the Tribunals Courts and Enforcement Act 2007.

The warrant is therefore a defective instrument.

Transport for London needs to re-apply for a new warrant specifying your brother’s current address (wherever that may be). Civil Procedure Rule 75.7(7).

You don't need to pay the debt on your brother's behalf.

Given that the registered keeper appears to have registered his vehicle at his brother's address, I cannot see how it could be argued that the warrant is a 'defective instrument'(whatever that may be).

The correct course of action here is for the vehicle keeper to submit forms PE2 and PE3 (Out of Time Statutory Declaration). He will need to explain why he registered the vehicle to his brothers address and most importantly, whether or not he collected the post etc. He will of course have to provide his current address on the forms and also confirm that he had amended his V5C (Log Book) to his current address.