Walsh returns to his role as DS Ronnie Brooks in the third series of the programme next month. He told What's On TV that he is thrilled with the viewers' response to the drama.
"It's been phenomenal really," he said. "I couldn't have wished for more."
He continued: "The show itself, globally as a brand, has set itself in stone and everyone said it was going to be difficult to try and emulate that as a brand in Britain. But it just really took off and I know ITV are really pleased.
"People watch it here and abroad and say it's a fantastic show and ask when the new series will be on. I'm very proud of it and very privileged to be a part of it."
However, Walsh revealed that starring in the show has one disadvantage.
"It's a nightmare for me because I end up putting on so much weight!" he quipped. "And I bulk up for the role anyway. And then I've to lose it all when we've finished filming so I can go and do my other stuff!"
Law & Order: UK begins its third run on September 9 at 9pm on ITV1.
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