Westwood had interested a number of other clubs since his departure from Hillsborough, including Town's Third Division rivals Huddersfield.

The 26-year-old former Crewe central defender had started 86 games for Wednesday after joining the Sheffield club from Bradford three years ago.

"He has played at First Division level all of his career and he has got a lot of pace," said Cobblers boss Martin Wilkinson.

"He gives us flexibility as he can play at full-back or in the centre of defence and every time he has moved in his career it has been for a big fee, so I'm delighted we have got him on a Bosman.

"Every player who comes here has to have ambition. Ashley is experienced but also young enough at 26 to still have that ambition and he has plenty of time ahead of him," Wilkinson told the club's website.

Westwood is set to link up with County on their pre-season training trip to the United States after passing a medical.