Harry Hadley enjoyed the shortest tenure of any properly-appointed Chesterfield manager. Having come to the club with two games remaining in the 1921-2 season, he was on his bike by the end of August, and it remains unclear as to whether he was around to have much influence on the playing and coaching side of the club.

A button-maker by trade, Hadley came to prominence with West Bromwich Albion as a methodical and well-organised wing-half. He won promotion to division one with The Baggies in 1902 and won his single England cap a year later. Short spells at Aston Villa and Nottingham Forest preceded a drop into the Southern League, with Southampton and Croydon Common.

When football resumed after the Great War Merthyr Town chose Hadley to manage their side and he remained at Penydarren Park until April 1922, when he resigned to take up Chesterfield's offer of their manager's job. He arrived at Saltergate with two games left in the 1921-2 season and these were both won, but over the summer there was some sort of (sadly undocumented) falling-out between the manager and his board of directors. Faction-fighting on the board had led to the departure of Hadley's predecessor and a continuance of this may have been an influence on his departure. The board may also have been unimpressed with Hadley's comments at a meeting with the Supporters' Club, where he informed a delighted audience that he was not the sort of manager to be bossed about by know-nothing directors.

A week or so later, the news of his going rocked the fanbase. The local paper reported only the fact of his going, with no attempt to explain his departure. He was reinstalled as Merthyr manager almost immediately but resigned again in October 1923. He enjoyed characteristically short-ish spells at Aberdare and Gillingham before going back to Merthyr for a third time. Later football involvement saw him scouting for Chelsea and managing Bangor City before he passed away in West Bromwich in 1942, at the age of 67.