By Naomi Clarke, PA Senior Entertainment Reporter Ant McPartlin and Declan Donnelly have kicked off the 20th series of Saturday Night Takeaway by reflecting on their first show over two decades ago. Saturday’s episode of the live variety show sees the return of popular segments including undercover prank, with music mogul Simon Cowell set to be the first victim. The Geordie duo will take a break from the show at the conclusion of the series, after saying the 20th “milestone” seemed like the “perfect time to pause for a little while and catch our breath”. Donnelly opened the show, saying: “Hell…