This must have been a specially modified F6 as the F6 never carried 230gal drop tanks in service
From the date, I suspect it was XF374, which Hawkers retained for a while as a development aircraft. I have an undated photo of it at Dunsfold with that tank fit, but no brake chute fairing. Whichever airframe Hugh used, it must have been very clean and highly polished to get 3hr 19min!
The other reason the standard F6 did not carry the 230 gallon tanks is that the flaps needed the outboard corners cut back for the big tanks.