The 23-year-old has accepted an offer of full-time football with Portadown in the NIFL (Northern Ireland) Premiership.

The midfielder made 47 appearances in all competitions last season and was one of Boro's most consistent performers.

Donnellan signed for Harrow in November 2019 following short spells with Hayes & Yeading United and Hitchin Town.

A former Queens Park Rangers youth team player and Republic of Ireland under-18 international, his previous clubs include Dagenham & Redbridge and Maidstone United.

He is the son of former Fulham and Chelsea player, Leo Donnellan Snr and brother of Maidenhead United defender Shaun Donnellan.

Harrow manager Steve Baker told his club’s website: “I’m really disappointed to lose Leo as he had a really good first season with us last year.

“He said he would definitely return for this season unless he got a full-time offer, and over the weekend he did. Ultimately, it’s an opportunity he can’t turn down and I fully respect his decision. We wish him all the best for the future”.