Pakistan captain Misbahul Haq said his century against England at Lord's on Thursday was the "top innings" of an impressive Test career.

The 42-year-old Misbah became the sixth oldest player in Test history to make a century as his unbeaten 110 took Pakistan to 282 for six at stumps on the first day of a four-match series.

Thursday's match was Misbah's maiden Test at Lord's, selection decisions having seen him miss previous tours of England, yet he secured a coveted place on the dressing room honours board at the very first attempt.

As soon as he had completed his 10th Test century, Misbah dropped to the turf.

But rather than utter a prayer, Misbah performed several press-ups, just as 73-year-old actor Jack Palance did when winning the Best Supporting Actor Oscar at the 1992 Academy awards.

But Misbah's celebration, which included a salute to the Pakistan flag flying above the Pavilion, was no tribute act.

Rather it was a reference to Pakistan's gruelling pre-tour boot camp at a military academy in Kakul in May.

"I promised the army guys I would do the push-ups if I got a century," Misbah told reporters after stumps.

"We had an honour code on the boot camp, for push-ups, so that was my promise to them the next time I scored 100. So that was for them, and the salute was for the flag."

Misbah equalled West Indies great Vivian Richards's then world record for the fastest-ever Test century with a blistering 56-ball hundred against Australia in Abu Dhabi in 2014 -- a mark surpassed by Brendon McCullum's 54-ball hundred for New Zealand against Australia at Christchurch in February.

But Thursday's hundred ranked higher in Misbah's estimations.

"I rate this as my top innings in Test cricket and I'm really happy about that," he said.

"It's a dream to play at Lord's and especially getting 100, and the name on the honours board is something special," added Misbah, who vindicated his own decision to bat first after winning the toss.

"Obviously when you are playing competitive cricket you just don't think about your age.

"If you are there, you just take on the challenge that comes with playing the game.

"These records are always something special, and they are very satisfying to make those kinds of achievements, but the main thing is just to keep achieving for your country."