I used everything that Harry could tell me in my own work. I'm sure Nigel or Martin could share more insights. They knew Harry and either had more time with him. I only exchanged emails and a couple of letters.
I also drew from Harry's contributions in Rocky Chandler's series, Death From Afar. Harry wrote a lot of snippets (tips) that Chandler published and I republished them (Fair Use Doctrine).
Harry told me he used to carry that Commando knife on his lower leg. Then during Market Garden his company advanced and he noticed his knife was missing. He backtracked and luckily found it sticking up in the grass. He did some horsetrading with an American paratrooper for a bayonet sheath and thereafter carried the knife in the bayonet sheath (which was worn on his belt).