The 36 year old’s seven under par round contained six birdies, one bogey and an eagle three at the long 14th.
Starting on the back nine, Kjeldsen turned in 32 before holing a long putt from off the green for birdie at the par three third.
His only dropped shot of the day came at the fifth, but he got it straight back at the next, chipped out the bunker to two feet for birdie at the long seventh and finished with a 20 foot birdie at the ninth.
The three-time European Tour winner held a one shot lead over Sweden’s Joakim Lagergren and South Africa’s Alex Haindl, who still had three holes left to play.
Ireland’s Shane Lowry, Scotland’s Alastair Forsyth and Australian Richard Green were all in the clubhouse with five under par rounds of 67, while Alvaro Velasco, Craig Lee and Sihwan Kim were on the same mark out on the course.
Italian favourite Matteo Manassero birdied the ninth, his last, from ten feet for a level par 72, while two-time Major winner John Daly went one better with a 71.
“I played great,” said Kjeldsen, who finished fifth in the Omega Dubai Desert Classic on his last European Tour start. “I haven’t played an official event since Dubai, where I played well. So it’s been a while, but fortunately the weather’s been good in London, so I’ve been able to practice a lot.
“My practice has been great, as it had been in Dubai, and I played well enough on my comeback at the Tavistock Cup last week. So I’m really pleased to have played as well as I did today, because my game felt like it did in Dubai, even though I hadn’t played much competitive golf since.”
As the afternoon session unfolded Ireland’s Peter Lawrie threatened to make Kjeldsen’s course record short lived.
The 37 year old, chasing a first win for four years on The European Tour, had six birdies in his first 11 holes to share second with Haindl and Lagergren.
England’s Richard McEvoy and Welshman Jamie Donaldson were both five under with five to play – the latter chasing a first European Tour title in his 249th event having finished third last week in Morocco, his 32nd top-ten finish.