Sanchez Watt respectively but there was relief when Hayden passed up a glorious opportunity to give the hosts the lead by side-footing wide of an inviting target.
Thorpe looped a speculative effort over the top before McGinty was booked for a foul that almost led to further punishment as Henderson beat Gollini with the free-kick but the bar came to United's rescue. It proved to be only a stay of execution as Arsenal dominated the possession in the closing stages and snatched a winner when Bellerin beat Lingard to a loose ball just outside the area and swerved a volley past Gollini.
There was controversy at the death when Bellerin blotted his copybook with a poor challenge on Ekangamene. Incredibly, it was the United scorer who was booked for complaining rather than the adventurous full-back.
United: Gollini; Vermijl, Thorpe, McGinty, Büttner (Fornasier 46); Cole, Veseli, Tunnicliffe, Ekangamene, Lingard; Januzaj. Subs: Blackett, Sutherland, Cofie, Daehli.