Dele Alli (£5m, MK Dons to Tottenham, 2015)

Dele Alli

Denying the existence of an English tax on footballers would be futile: it’s real, and the army of generic homegrown players who have moved for extraordinary fees proves it.

The balancing factor, in this case at least, is residual snobbery towards the Football League. Alli was clearly a very talented player and will likely become one of the most successful of his generation, but appearing in League One somehow counted against him.

For context, in the same transfer window, Tottenham recouped the fee for Alli by selling full-back Kyle Naughton to Swansea. 

Ryan Bertrand (£10m, Chelsea to Southampton, 2015)

Ryan Bertrand

Wastage at one club leads to opportunity for another, a theory which might be further proved if Chelsea graduates Nathaniel Chalobah and Dominic Solanke are successful at their new clubs (Watford and Liverpool respectively). 

Bertrand, who had initially joined Southampton on loan, was an early example of what happens when a developing player is starved of first-team minutes. He fails to develop at a proper pace, decides to leave, and is then invariably sold for far less than his potential value.

Two years have passed since then and a new television deal has swollen the market further, but - given that Bertrand is now being hunted by Manchester City and Liverpool - it remains a pertinent example of big-club oversight.

Fernando Llorente (£5m, Sevilla to Swansea, 2016)

Fernando Llorente

Undisclosed transfer fees are joyless and, at a time when transparency is particularly important, they really shouldn't be allowed. However, Llorente’s fee is assumed to have been minimal, and it could easily be argued that he was one of the 2016/17 Premier League’s most valuable players.

His wages probably aren’t incidental, but without his 15 goals from 33 league games last year, Swansea would have been relegated. Clearly, that left them at a net profit for a player who outperformed many of the forwards who cost considerably more.

Demarai Gray (£3.7m, Birmingham to Leicester, 2016)

Demarai Gray

An odd transfer and a stranger state of affairs. Gray was a known commodity before moving to Leicester, having been a fixture in the England age-group teams as a teeenager. Given his obvious promise, £3.7m was an absurd fee and asked serious questions of whoever allowed such a paltry release clause into his Birmingham contract.

To date, Gray can’t quite be said to have been a success at the King Power, but only a contrarian would deny that a surge is imminent. He’s grown frustrated with his lack of opportunities and, tellingly, Borussia Dortmund and Tottenham are watching that stand-off with interest. Either Leicester will get a very good player or make an extremely handsome profit. They've already turned down £20m from Bournemouth this summer.