Sky Bet League One leaders Birmingham avoided a FA Cup upset with a 1-0 win at non-league Sutton.

Willum Willumsson’s first-half goal was enough to beat the battling Vanarama National League outfit, who rarely troubled the visitors.

Birmingham dominated possession for long spells, but apart from a Jay Stansfield shot that was well saved by Jack Sims, they failed to create many clear cut chances in the early exchanges.

The Blues broke the deadlock in the 34th minute when Willumsson met a cross from Paik Seung-Ho with a volley.

Sutton squandered a glorious opportunity to level when Jayden Harris intercepted a pass and burst clear before firing wide.

That was as close as the U’s got as Birmingham shut the game out in the second half.

Luke Harris saw an effort beat away by Sims and Sutton substitute Ashley Nadesan could have forced extra-time, but his volley bounced into the ground and over the bar.