Bellingham, along with his parents, visited United’s Carrington training base in March 2020.
However, despite their efforts, the Red Devils were usurped by Borussia Dortmund who later sold him to Real Madrid for £88.5million.
Bellingham has gone on to become a key figure for both club and country, and is set to play a big role for England at Euro 2024.
His progress has left United with a real sense of what could have been, having offered Birmingham £30m in January 2020.
United have lacked a midfield general but could have potentially landed the 20-year-old if not for a “rubbish” pitch.
Robson and Cantona have taken the blame for failing to convince Bellingham that Old Trafford should’ve been his next home.
Robson – who made 300 appearances for United – admitted that the pair thought Bellingham would sign on the dotted line.
Robson told The Telegraph: “It was really disappointing. We were at Carrington and Sir Alex Ferguson was there a little earlier than I was.
“Eric and I met him, and his mum and dad, and we were chatting away.
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“It was really looking promising that he was going to be signing for Manchester United… me and Eric did a rubbish job as he signed for Borussia! We thought we had him in the bag!”
Reports have also suggested that football director John Murtough’s – who resigned this week – was partly to blame for United not landing Bellingham.
Murtough reportedly could have made a more compelling case for first-team minutes – a factor which was clearly hugely important to the youngster.
Bellingham, of course, joined Dortmund instead and excelled in Germany before featuring as captain at aged 19.
Since joining Real Madrid in the summer, he has scored 16 goals from 23 LaLiga appearances.
Meanwhile, Robson, 67, beamed over the impressive performances of United starlet Kobbie Mainoo.
He added: “I love the lad’s temperament. I see him at the training ground and he is always polite to everyone. That is a great start.”
Mainoo, 18, is set to sign a bumper new contract in the summer.