That's really sad. I loved GTP/Group C racing in the 1980s, with the XJRs (both Group 44 and TWR) battle it out with the ubiquitous Porsche 962s. I was glued to the TV in 1988 when Jan Lammers won Le Mans in a TWR XJR-9LM. I've got a Corgi die-cast XJR-9 on my desk (though in Castrol livery, not the purple Silk Cut livery of the Le Mans winning car).
Rest in Peace, Mr. Walkinshaw. I thank you for all the thrills and excitement your cars and your team brought me in my youth.