Joe Root said his first day in the job as England captain was one that left him in “dreamworld” after delivering an unbeaten 184 that was masterful in its execution and powered his side to a position of dominance over South Africa.

Root, who became the sixth England captain to score a century during his first Test in charge, arrived at the crease 27 minutes into play with the score a worrying 17 for two. But after six hours of batting he found himself walking through the Lord’s pavilion to a resounding ovation, with the total swelled to 357 for five.

Speaking after stumps, with his voice hoarse from a cold, the 26‑year‑old Root said: “It was pretty special. I’m in a bit of a dreamworld, to be honest. I’m a little bit bunged up but I’m making the most of it. I felt pretty groggy when I woke up in the morning but there was nothing stopping me enjoying the day. It’s a privilege to be England captain and I wanted to make the most of it – a cold wasn’t going to get in the way.”

There was fortune along the way for the new captain. While he put on stands of 114 with his vice-captain, Ben Stokes (56), and an unbroken one of 167 alongside Moeen Ali (61 not out), two chances were offered early in his innings. A top-edge on five sailed over an ill-stationed long leg, before JP Duminy failed to cling on to a flashing edge at gully on 16.

“It seemed to all fall into place – when you get a life early you feel like it is your day. Hopefully it’s not the end, I can push on and make a really big score,” said Root, who during a run-soaked evening session passed the 173 made by his predecessor Alastair Cook against Bangladesh in 2010 – the previous best by an England captain in his first Test.

“I heard whispers of [that record] and it’s a nice touch but it will mean more if we get a positive result from the game. You want to set the example – a message to the guys – and show you are willing to do it yourself. Being brutally honest, I was quite surprised myself how normal it felt when I got out there, it terms of how I went about things. Maybe that’s the first day in the job but I’d like to think it’s in my nature to play to that accordingly.”

Root’s third slice of luck came when he was stumped on 149 off a no-ball from the spinner Keshav Maharaj – “it’s a nice feeling getting that call back after a glaring error like that” – in what was the second such infringement by a South African bowler; Morne Morkel had earlier bowled Stokes on 44 only to discover he had over-stepped by some distance.

Vernon Philander, the pick of the bowlers with three for 46, said: “There’s probably no excuse for that – the guys overstepped and it cost us wickets. We could have turned things round had we got Root there, but the frustration is the same if it is a spinner or seamer. It was just a poor day in the field overall.”