That sounds like the UK version of 4E. I only came to it with 5E. I remember finding a 'supplement' that was obviously for an earlier edition mixed in with my dad's stock at one point, but it'd be gone now. rpggeek.com/image/285321...

Tunnels & Trolls (Fourth Edition)

T&T Front Cover UK Edition - Second Printing Jan 1980

Yep, that's the one 😍 the binding on mine was different, kind of A4 folded and stapled, without the black edge.