I concur with the remarks about the jump seat. I did one trip from CDG to Heathrow, then later a Larnaca return trip as ATCO Fam Flights.
When the RAF first bought them, the first one was brought to Farnborough to check its IR signature and (possibly) for ECM fit? The IR signature checkout consisted of a number of runs for the boffins along the runway down to about 100ft! Awesome. I think it then went to Marshalls for 'militarisation'.