Isn't it what's below the Donut that makes it difficult to redevelop? To me, as an outside, Chesterfield appears to have escaped the worst of the 60-70's 'nuclear bunker' style of architecture - Casa Hotel excepted.
Not aware of any problems under the Donut, Big Dave, I lived in that area in the 1950s and there were houses, shops, pubs, offices, light industrial yards, garages, council yard, Quakers chapel and graveyard etc., but would welcome info., regarding that. Initially the telephone exchange was to be sited there, then bus station and recently a shopping complex?, nothing happened, still a car park.
We would have had a "bunker" style development in the 60s if (was it Hammersons? / council ) had their way, it would have obliterated the town centre. Public opinion changed that, which resulted in a rethink and the Pavements as it is now, was created, keeping the main frontages.