Leeds United's 1973 kit, produced by Admiral, is often cited as the first official adult replica kit sold by a club to the general public, although it was initially only available in children's sizes. This landmark deal between Leeds manager Don Revie and Admiral owner Bert Patrick reportedly involved Admiral paying Leeds £7,000 to feature their logo on a redesigned kit.
Following Leeds' pioneering move, the trend for replica kits quickly grew. By the 1977-78 season, 84 of the 92 clubs in the English Football League had prominent manufacturer logos and offered children's replica kits. In Scotland, Umbro sold Rangers and Celtic shirts, while Adidas sold Aberdeen and Dundee United replicas that same year.
Before this, unofficial youth sets, such as Umbrosets featuring Manchester United in 1959, were available. However, these were not considered true replicas akin to those worn by players. The 1968 Design Copyright Act, which regulated the production of registered designs, may have contributed to the delay in clubs and brands exploring replica kit sales in the UK.
Academic research examining crowd photos from the 1960s found no evidence of replica shirts being worn by adult or child fans as matchday apparel until the mid-1970s, and then primarily by male fans at cup finals. The first adult replica shirt for England was Admiral's World Cup 1982 kit.