Karthikeyan seemed at home with the Brands Hatch circuit, where he had won a couple of F3 titles earlier.
The former F1 racer drove a fantastic Feature race to take India from seventh to fourth place to secure the team's best ever finish in this World Cup of Motorsport.
Team Germany won the Feature Race, followed by Great Britain and Italy, with just three tenths of a second separating Karthikeyan from a third place finish after 70 minutes of racing.
A1 Team Italy, however, were under investigation for pitting after the safety car had been called.
After Team India had qualified fifth for the 20 minute Sprint race, Karthikeyan took his place between Italy and Malaysia for the rolling start. As the 22 cars thundered down the line to start the first lap, Karthikeyan lost two places to Malaysia and the Netherlands.
With the race consisting of just 15 laps, the team had little opportunity to make up the position, despite looking considerably faster than the orange Dutch car. Karthikeyan went on to cross the line in seventh, just one place out of the points.
Taking the finishing position from the Sprint race as its starting position for the Feature race grid, the Indian car had a good start off the line and was running alongside the Dutch car into the first corner with the Irish car close behind.
As the cars entered the narrow right hand bend, Karthikeyan ran out of room and had to slot in behind the Netherlands and Ireland, in seventh place.
A1 Team India chose to make their mandatory pit stop early in the race, a move which paid off when several teams were caught out by a safety car period which closed up the field. When all the A1GP cars had pitted, India came out in fourth, close behind A1 Team Italy.
Karthikeyan fought hard to take the last spot on the podium, putting Italy under pressure lap after lap. But with little opportunity to overtake, India had to be happy with fourth position.
Karthikeyan was pleased to secure seven points but also frustrated to have missed out on a podium finish.
"We were fourth, we could have been third, we had the pace for third and it would have been great to get a podium in the last race of the season.
"There was some controversy as to whether Italy pitted under the safety car, which is against the regulations, but in this instance no action was taken against them, so we have to be happy with fourth," a dejected Karthikeyan said.
"It's very difficult to pass here, apart from Druids, there really isn't enough room. When I closed up on Italy I started suffering from understeer which made it difficult to stay close. But it was a decent result today and that's good for the future."
A1 Team India seatholder Yohann Setna shared the racer's feelings and said, "I'm pleased with the result; fourth is India's best ever finish, but I'm sad to have missed out on a podium.
"We believe Italy pitted after the safety car was called, but there isn't much we can do about that. We'll get a podium in five months time when the new season starts in Zandvoort. It motivates us to work hard over the summer and get things sorted."
The A1 Team India car will now be tested to ensure it is in the best possible condition for the third season of A1GP. The team will not be on track until the collective test on August 28-29 before the season opener on September 30 at Zandvoort Circuit Park in the Netherlands.
Sundar meets Karthikeyan at the Australian GP
A1GP: Karthikeyan disappoints