Beckham also said how he'd taken a look at his eldest son's wardrobe for ideas: "A lot of the details on the clothing are probably from my wardrobe and Brooklyn's wardrobe, so it's really cool."
Even though the biggest thing in his life is football, the top sportsman says he's always liked to wear unual clothes.
"I've always been into fashion, and I've always liked to dress that little bit different - you probably heard about the page boy outfit," laughed David.
In the last few years M&S has had real problems getting people to buy their clothes. This is their latest attempt to attract people back into their shops.
M&S say David is a "style icon and role model" and that's why they chose him.
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