Found this whilst trolling Google flights earlier today:
https://www.google.com/flights?lite=...2*2.CAD.486782
The Europe portion ARN-> LHR is just in J since sadly BA doesn't offer F service in that region. The long haul portion is LHR->SFO is however in F on a 747! I suspect this might be a good deal, although BA has been known to post some crazy F fares over the past couple of months. Availability seems to be Tues/Weds in March,April,May,...
Look forward to hearing the community's feedback on this.
Safe Travels,
James