Checked in at LHR for my flight to EWR, and onto SFO followed by SIN (via NRT!) and HKG.

Had a very friendly and helpful agent in London who took the system wide off me, and when I asked her to document it in the record, she smiled and reassured me that it was something she always did! Got the boarding passes for the flights to EWR and SFO.

At SFO, the agent had never heard of system wides, but could see the note on the record. He got some assistance from the supervisor, who showed him what the sw meant and that London had indeed put the cert no into each segment - she was so amazed that someone had done it correctly for once! Out popped my 3 remaining boarding cards.

The journey takes around 3-4 days (give or take an hour or two of delays and the dateline!).