It is felt now that Mourinho would have had a greater impact if he had directly followed Ferguson.

For a start, his personality suggested he would have taken on the task of succeeding the Scot by believing he could do better.

Whereas under Moyes, there was hesitation in the transfer market, it is hard to imagine Mourinho being similarly reluctant to execute deals.

Thiago Alcantara’s agreed move from Barcelona would have been completed, sources stress.

United would also have avoided the mess they got into around Marouane Fellaini – who moved from Everton for £27.5m on deadline day, but only after the club had missed out on a lower release fee.

Fellaini, it is claimed, simply would not have been signed.

Mourinho went so far as giving United his view on a number of players, including Italy midfielder Daniele de Rossi.

Not only it is safe to assume Mourinho would have signed players, the feeling is he would also have got more from the experienced ones he was inheriting.

It is generally accepted now that no-one could have extracted more from Ferguson’s final title-winning squad than the Scot, and they significantly overperformed. But the fall off, to seventh, was dramatic and unexpected.

Even the players themselves have struggled to identify specific reasons. The feeling remains that Mourinho’s presence would have pushed them.

With clarity and expression, Ferguson uses the documentary to recount Mourinho’s tears as he explained why he could not join.

It was a huge blow to Manchester United. Arguably, they are still to fully recover.