https://www.bbc.com/sport/football/61648608
Charles Reep: The military accountant who brought data analysis to English game
IMO he was another misunderstood visionary in the game ahead of his time and not only the father of game analysis, but also another example of how clueless The FA have been (and still are?).
IIRC The FA wrongly used his '3 pass theory' and his association with Cullis' Wolves (and their very hard working and high intensity style of play), to promote Route 1 / long ball tactics in their coaching manuals (along with lots of end to end running), as being the cornerstone of The English Game (coming after Wolves success against European champions in what was the fore-runner of the UEFA comps.
IMO they misunderstood his analysis every bit as badly as they misunderstood Chapman's version of the 'WM', as in both cases they took the long deliberate passing from deep to the flanks as simply being a long kick forward from Defence = hoof-ball. Even with Wolves being ahead of their time in terms of fitness was seen as being the objective and not the means to be able to out number opponents in attack, as well as getting numbers back to defend. They further ignored that Reep had implemented a style of play based on his analysis of Chapman's Arsenal, and failed to recognise the impact of those tactics at the various teams he had been associated with prior to Wolves.
They later further misunderstood Taylor's use of the similar style at Watford and were still promoting long ball tactics in their coaching manuals as late as the 1990s, although at that point the 3 pass theory had evolved into a 5 pass theory but still based upon long balls out from Defence, and playing 442 with lots of running/work rate.
Perhaps the biggest error made and most significant point missed by most at the time in Reeps analysis (and the crucial aspect to his 3 pass theory), was the omission made regarding winning the ball back in the finals 1/4 of the pitch = in and around the opposition area = essentially a high counter-press. The '3 pass theory' was based upon being the most efficient way to score goals, and it stemmed from winning the ball high up the pitch rather than covering the length of the pitch. Efficiency and fitness/work rate were fundamental to the average number of chances that needed to be created to have the number of shots at goal to score.
In some ways Reep's work may not have been totally ignored, as elements of his analysis and components of his theories / tactics can be seen in the work of Jimmy Hogan with The Mighty Magyars, and then again later with 'Total Football' and Cruyff's impact as both player and manager and still now with Guardiola.
IMO the error/s made by The FA undid the success of Ramsey's Wingless Wonders in winning the WC, and possibly put the development of the domestic game back some number of decades behind where it could have been. The one person I credit with doing much to correct this (and to bring The English Game in line with the modern thinking and tactics), was our own AW.