Bristol City have signed Republic of Ireland Under-21 defender Derrick Williams from Aston Villa.
The versatile defender, who can play at centre-half or left-back, joins the League One club on a three-year deal.
Williams made his senior Villa debut last season and, according to his new club's website, he turned down a new deal in favour of a move.
"I needed to take this step," he told the Villa website. "I hope it's the right decision.
"I want to make a career for myself and I'm grateful for the great start I've been given by Aston Villa and coming through the Villa Academy.
"Bristol City were interested and it's a big club. I'm looking forward to the challenge.
"I have no issues dropping down to League One. The club's aim is to bounce back stronger and it's a great goal to have."
The 35-year-old, who spent a loan spell at Sixfields in 2011/12, has penned a two-year contract with effect from July 1.
"Matt was always our number one keeping target this summer and I am delighted we have got him," Cobblers boss Aidy Boothroyd told the club's official website.
"I am really pleased that in each of the last two seasons we have got our top goalkeeping targets.
"We have done well to get Matt. We wanted an experienced keeper and Matt fits the bill perfectly.
"We know he will settle in quickly as he knows the club and he knows the staff and I think he will be another excellent addition to the squad."
