The SEN model was HZ-123 Saudi Royal Family; I believe the a/c had become redundant but as part of the Hawk deal it was fully refurbished at Southend as a gift for the King who died during the refurb period.
Its last Saudi role was use for the Saudi Ambassador to the UN. The aircraft was refurbed some years ago at SEN and then flown back to the collection via several stops that it needed to make and also had been serviced at its time with Qantas.
HZ-123 having been parked untouched for nearly 10 years was back in the air after 3 months. I must be assume that JT's is in far better condition. I believe that there is footage of the SEN exercise on U-tube.