This is a seat allocated as part of the rather generous BA flight crew agreement which provides them with a rest space (in addition to their in-flight beds). However, 61B could well be a very decent revenue earner as stated by Martyn and is actually rarely occupied by flight crew and ends up being one enormous red herring for BA.
A major bugbear is the frequent upgrading of their pals and family to this seat (and I do not believe cabin crew are involved as they do not currently indulge in staff travel). I have been sat in 60 A and actually begun a conversation with one of those friends of flight deck. And as a matter of note, the flight was extremely full, so it could well have been sold.
It seems BA bend over backward for its flight crew and this is yet another example. I suggest a revision of their earnings and agreements to bring those in line with industry averages.