It all started behind a pine tree.The setting was Middlesbrough’s Rockliffe Park training ground, two days before the club were due to meet Southampton in the Championship play-off semi-finals.Will Salt, a first team performance analyst intern working for Southampton, had travelled north to gather intelligence on the club’s opponents as they trained a few metres away beyond a metal fence. He stationed himself behind the tree and got out his mobile phone to record Middlesbrough’s players, hoping he would go unnoticed.It didn’t work. Salt was spotted and, while he quickly made his escape, he had sparked into motion a story which must now rank as one of the most extraordinary in the history of the English Football League.The view Will Salt had from behind the pine tree outside Middlesbrough’s training ground (Phil Buckingham/The Athletic)It culminated on Tuesday with Southampton being expelled from the Championship play-off final. Middlesbrough, who they defeated in the semi-final, will now play Hull City on Saturday in a match worth around £200million, the rough value of a place in the Premier League.After they admitted to spying on Middlesbrough, as well as Oxford United and Ipswich Town earlier in the season, Southampton were also given a four-point deduction that applies to next season in the Championship. The club has lodged an appeal, which will be heard by one senior judge today. The panel’s decision could yet be reversed.It has also emerged that: