Originally Posted by
ThatT1Feeling
I was told yesterday at an F checkin desk that it's always possible as long as the bag would ordinarily be small enough to be taken into the cabin (i.e. hand baggage size).
Yes, as noted for LHR (and NCL pretty much always did it). And previously LGW but LCY never allowed it, nor did most out-stations on the mainland and Ireland. Again it's a policy waiver and doesn't allow for more cabin bags than your allowance. You can add bags to an HBO fare online in both MMB and OLCI.