Their relationship appeared to turn sour after he quit One Direction in 2015, with Bradley now revealing Simon was rather on the smug side when he learned Bradley had the biggest selling debut album of last year, over Zayn’s ‘Mind Of Mine’.
Speaking to The Guardian, Bradley revealed one of Zayn’s ex-bandmates also found the sales figures amusing.
The music mogul was responsible for the early days of Zayn’s success, having initially spotted him at the auditions for ‘The X Factor’ and mentored him throughout his time in One Direction.
After Zayn quit the group and signed to a rival label, their relationship has since soured.
Bradley released his debut album - ‘Chasing Dreams’, a collection of swing standards and original material - in 2016.
Zayn’s debut album came earlier in the year, led by the chart-topping single ‘Pillowtalk’, which achieved what 1D never managed when it hit number one on both sides of the Atlantic.
More recently, Zayn has collaborated with Chris Brown, M.I.A. and Taylor Swift, the latter being on a duet taken from the ‘Fifty Shades Darker’ soundtrack.