As a layman, I don't claim to have an authorative view on this, but I wonder if NickB or another lawyer would?

Hak has a contract with the airline and his fight is cancelled, the airline re-books him, but fails to re-issue his ticket in time to make his new flight. Would this fall under either of the categories of beach of contract or negligence?

If so, given that the airline has either breached contract or been negligent, does Hak have a case for his consequential loss?

It seems the airline is trying to benefit by charging him GBP2,000 more for a circumstance arising from their negligence or breach and this seems contrary to common sense (but I am not a lawyer.)

Also, I wonder if EU261/2004 could be made to fit such a situation, wrt to re-routing? I guess that would depend on one's view of Hak's final destination.

Regardless of the above, it looks like a lousy way to treat a premium customer, but does not surprise me, as I have had lousy ground service at Heathrow (from BA, also other airlines) on may occasions. Golden geese come to mind and it seems crazy that, in this online world, the ticket cannot be issued remotely and sent to the pax's smartphone, the baggage re-routed and the pax able to return to the restricted area and go to the gate.