p21 of
http://www.caa.co.uk/docs/33/srg_gad_gasil2002_01.pdf says:
"The wing spar centre section joint limits the fatigue life of the Bulldog, and the aircraft must be grounded when a fatigue index (FI) of 114 is reached.
The airframe is however, capable of continuing in service until a FI of 200 is reached, provided the wing spar centre section joint is modified (BAE SYSTEMS modification BH193) to ensure compliance with CAA Airworthiness Directive 004-07-2001."
"Where an [Bulldog] aircraft has never been fitted with a fatigue meter, the wing spar centre section joint fatigue life limit is reached at 5000 flying hours. If the wing spar centre section joint is modified, then the aircraft can continue in service until 8760 hours. All the above information is more fully described in mandatory service bulletin BDG/100/170."
The Dog in question has
8639hrs.