Morecambe’s promotion hero sealed a move to the Championship side on Saturday, ending weeks of speculation surrounding his future.
Lee Johnson’s side were among the teams – including Rangers and Hull City – reportedly keen on the 22-year-old before he moved to Kenilworth Road.
Hatters assistant boss Harford revealed: “It is a signing that numerous other clubs were beaten to, so I hope that is what makes it even better.
'Sublime': Phil Smith's Sunderland player ratings after Seny Dieng's late equaliser for QPR
'Should have been sent off' - Sunderland fans fume at Ilias Chair as QPR goalkeeper Seny Deng scores
Sunderland 2 QPR 2: Highlights after Seny Dieng’s equaliser plus Ross Stewart and Ellis Simms goals
Sunderland boss Alex Neil issues worrying Dan Ballard injury update and explains his Luke O'Nien call
Championship news: Sunderland’s rivals set to lose striker as Leicester City sign goalkeeper amid Daniel Iversen speculation
"We’re signing a really, really exciting player that can play across the front in any position, as a number ten, a striker and we believe he is going to excite the crowd.
“It is quite an exciting pre-season in terms of who we have tried to bring in and how we’re trying to evolve and take the club forward, with younger, more exciting players.”