Jack Leach says he "never thought" he would reach 100 Test wickets after bringing up a century during England's second Test against Pakistan.

The spinner crossed the mark with figures of 4-98 in Multan as the tourists forced a collapse from the hosts to bowl them all out for 202 on the second day.

Half-centuries for Ben Duckett and Harry Brook saw England reach stumps with a lead of 281, pushing them closer to a series victory on their first red-ball visit to the country since 2005.

Leach, who made his debut in 2018, has played 31 Tests for England, but remains surprised to have reached the magic milestone, given his struggles with Crohn's disease and other matters limiting his game.

"I never thought that would happen," he told Sky Sports. 

"It's crazy to think I've got 100 wickets in Test matches just because of how difficult I've found it at times.

"But then you realise there have been some good moments along the way, you do some good things. I definitely feel like I'm getting better as I play more, so that's pleasing."

Having seen Pakistan set off in pursuit of what looked like it would be a high first-innings total, Leach's spell with ball in hand was crucial to preventing fast progress and ensuring a lead for England.

"On these wickets, it's about being as patient as you can between those [sharply turning] deliveries," he added. 

"It's something I'll try to do better in the next innings, to patiently go about my work. 

"There's a bit more happening than in Rawalpindi so it is just looking to be patient and work your way through. It's really difficult.

"I think it's been a really good day for us. [We'll] look to get a few more [runs] tomorrow, then have another go at them. They [the England batters] played really, really well and put us in a good position."