The clue as to where this offer has gone is in the “2008” part of my post 😉
The offer is now back to the regular 6,000 BA Miles per Premium Plus card sign up, though you can get more BA Miles if you are referred by an existing cardholder.
Link to the (less good) current offer is below:
And, technically, the BA Miles are not free as I erroneously stated earlier, as the card has a fee of £130 per annum, however this is easily offset by the Amex 2for1 voucher you get after spending a certain amount (I think about £10k), which effectively doubles the value of you BA Miles when used exUK on BA metal.
So a return in First to San Francisco SFO costs 150,000 BA Miles for two people, vs. the usual requirement of 300,000 BA Miles without a 2for1 voucher.