Cobblers' boss, Colin Calderwood, has been a long time admirer of the midfielder and made initial enquiries over the summer, only to be knocked back. But it has become increasingly difficult for Williamson to hold down a first team place for Keith Curle's men, and so the Field Mill outfit decided to cash in.
Williamson becomes Cobblers' twelve signing this season, as Calderwood looks to bolster his squad and hopes to revive what has been a stuttering start.