The 27-year-old had not made a single top-flight appearance when he joined the Magpies in January, 2010, as a contractual wrangle had prevented him from turning out for his previous employers, Portsmouth.
He performed creditably in the second half of last season, as Newcastle cantered to the Championship title, but faced an uncertain future when Sol Campbell joined the Magpies last summer.
However, while Campbell has failed to force his way into the first-team this season, Williamson has started all bar seven of Newcastle's league games and will end the campaign as a seasoned Premier League centre-half.
"It's been a fantastic season for both me and the team," said the former Torquay trainee. "I came here to try to prove myself at this level and I wanted to play as regularly as I could.
"We all know the position the club was in when I joined. There are some very good players here and I'm very appreciative of the number of games I've been able to pull on the jersey this season.
"Since I came in last season there's been a winning mentality, and that's made it easy for people to fit in.
"I think the others players have looked after me and, like the team as a whole, I've enjoyed playing in the big matches. That's what it's all about."
Williamson's relationship with fellow defender Fabricio Coloccini has been one of the major factors behind Newcastle's success this season.
Tuesday's clean sheet against league leaders Manchester United was the duo's eighth shut-out of the season, and the pair seem to complement each other perfectly, with Coloccini's ease in possession blending with Williamson's obvious relish for a physical tussle.
"To play with somebody of Fabricio's talent is fantastic," said Williamson.
"To be able to work with him every day - it's a joy to play alongside him.
"It's amazing the ability he's got, and he's the nicest guy you'll ever meet. He's very warm and welcoming, and makes you feel part of it. Everyone knows his English isn't as fluent as most of the other lads, but he's a really nice, family-orientated guy.
"He's also a very cultured player, very laid back. He's very good on the ball. I play to my strengths - I try to be aggressive and win my headers, and I let him do the ball play!"
Tuesday's draw left Newcastle seven points clear of the relegation zone with five games remaining, but Williamson insists the Magpies cannot afford to relax ahead of today's game at Blackpool.
"It's important we approach the game with the same mentality as Manchester United," he said. "We can't take our foot off the gas, as has been the case at times this season.
"We've shown time and time again that, when we get the mentality right, we can beat anyone. But we need to play with the same tempo that we did on Tuesday and it's all about how we approach the game."