Harley joined the club from Aston Villa in the summer of 2021 and has been in and around the first team for the past two seasons. The left-back, who can also operate further forward as a wing-back or central midfielder, scored the first goal at Wembley against Birmingham City in the Vertu Trophy back in 2025. 

Mills credits his development to a loan spell at Enfield Town in September 2024. A committed player, Mills is a wholehearted performer, who likes to get forward and support the attack.