Sir Terry Leahy’s appearance on Panorama (BBC1, 8.30pm, 19 January) was always going to be one to watch. Leahy has kept his counsel ever since he left Tesco in 2011, watching silently from the sidelines as it slipped into total disarray, other than to acknowledge the worsening conditions for out of town supermarket locations due to soaring fuel pries.

This then, was a killer exclusive for Panorama. And to begin with they got what they came for, as Leahy took careful aim at his successor, Philip Clarke, and squeezed the trigger. But where the programme failed was the lack of any probing into Leahy’s own contribution to the chaos.

Leahy was in charge of Tesco for 14 years. He quadrupled its size from 600 stores to over 3,000. And he led it abroad, enjoying some success, but also a disastrous and expensive foray into the US with Fresh & Easy, which removed key execs like Tim Mason, and focus, from its core UK business.

Arguably its extreme acceleration, both at home and abroad, is at the root of Tesco’s problems as it continues to lurch from one calamity to the next today. Certainly it made it unpopular with a public fast becoming sick of the sight of a new Tesco.

So, for me, Leahy is wrong to blame Tesco’s tailspin solely on Clarke, even if his three years at the top felt like a troubled reign. And although Panorama was excellent in parts - particularly over Tesco’s ongoing abuse of suppliers - the show failed to challenge Leahy on any of it. And as interesting as the show was, that felt like a wasted opportunity.