It was the morning of Thursday, 7 May.

Middlesbrough were at their Rockliffe Park training base preparing for the game against Southampton 48 hours later.

The spy – Southampton intern William Salt – is said to have parked at the golf club, then walked a couple of hundred yards down a road that leads to a raised area of ground.

Sources told the BBC that Salt stood pointing his mobile at the training session, while wearing in-ear headphones.

Middlesbrough staff believe he may have been live-streaming the session via a video call.

A member of Middlesbrough’s staff approached, say BBC sources, but the person would not identify himself. He then quickly deleted some content on his phone before running into the golf club.

He jogged into the toilets, changed his clothes and hurriedly left the site.

Middlesbrough’s photographer took photos and matched him to a photo on the Southampton website. One of those pictures was subsequently made public.

Boro were furious and quickly reported the incident to the EFL, which charged Southampton with breaking two regulations:

EFL regulation 3.4, which requires clubs to act towards each other with the utmost good faith; and

EFL regulation 127, which prohibits any club from observing, or attempting to observe, another club’s training session within 72 hours of a scheduled match between the two clubs.

During the investigation, details emerged about the club watching training sessions involving Oxford and Ipswich, in addition to filming Middlesbrough as they prepared for the first leg of their play-off semi-final.

Southampton did not win any of the three games – they lost 2-1 at Oxford, drew 2-2 at home to Ipswich and 0-0 at Boro.

Salt has since been appointed to a permanent role at Saints in the club’s academy.

Southampton told the BBC “he’s been through a time time”.

“When your photo is put out to the public, that is something tough to deal with,” chief executive Phil Parsons told the BBC last month.

“A lot of people probably underestimated how that could have impacted a young lad so we’ve got a job to make sure that he’s looked after in his early career. But he’s a talented boy as well. I get good feedback and he’s got a good role at the club.”