Originally Posted by
LeisureFirst
Nothing remotely as complicated as this is required.
If you have access to his username and password, then you can log into his account and use it to book tickets for yourself. (The taxes and fees would presumably be paid with your own credit card, which wouldn't match his name, but that can't be the first time that's been done and it isn't against the rules in itself.)
...and he cancels the flights, keeps the miles and your £2250 and removes you from the HHA, unless you change his details and login.
He's selling Tesco vouchers for a Siblu holiday as well.
Big change of plans then!