Harrison Dunk scored at the very death to earn Cambridge a 1-0 win against Stevenage.In the seventh minute of added time, Dunk nodded home from close range following debutant Rory Gaffney's pinpoint cross.Substitute Gaffney was making his first appearance after regaining fitness having signed back in January, and had already forced a fine parry from Jesse Joronen.Charlie Lee almost gave the visitors the lead inside the first five minutes, heading Stephen Schumacher's cross on to the underside of Chris Dunn's bar.Cambridge forward Robbie Simpson drew a good save from Joronen after 22 minutes when he ran on to a loose defensive header, while the Stevenage goalkeeper made an excellent reaction stop from Liam Hughes following Luke Berry's corner.Moments before half-time Tom Hitchcock went close for Stevenage, heading wide when well placed from Lee's centre.In the closing stages Jordan Chiedozie headed wide and Berry flicked an effort just off target from Gaffney's cross.Dipo Akinyemi could have stolen the win for Stevenage in stoppage time but prodded wide before Dunk's decisive intervention.