On Flight Global. Presumably somewhere in the depths of PPRuNe there is a relevant thread, but the forum search engine did not turn it up.
RAF receives first C-130J with replacement centre wingbox
The first of 14 UK Royal Air Force (RAF) Lockheed Martin C-130J-30 tactical transports to undergo a life-extending centre wingbox replacement has been returned to squadron use at the service’s Brize Norton base in Oxfordshire.
Performed at UK C-130J design authority Marshall Aerospace and Defence Group’s Cambridge airport site in the east of England, the work “will enable the RAF fleet to remain in operation until 2035 and beyond”, the company says.
The UK Ministry of Defence (MoD) placed a £110 million ($144 million) contract in July 2017 for the modification, which is conducted using Lockheed-produced kits. The structural enhancement “extends the service life of the centre wingbox by up to three times”, Marshall says.
A 23-year-old example, the lead C4-model airframe (ZH867) underwent the work “in parallel with scheduled maintenance, to maximise fleet availability”, the company says. “Modification of the second aircraft is already well under way,” it adds.