Earl Bamber is a surprise late entry for the last two rounds of the International Toyota Racing Series, which culminates in the New Zealand Grand Prix at Manfeild next weekend.

The Wanganui driver, who won last year's NZGP but was pipped for the series championship by teenager Mitch Evans, will be in veteran Kenny Smith's car in the third round at Hampton Downs this weekend.

He said getting opportunity to get back behind the wheel was "completely unexpected".

He had gone to the Waikato circuit to give Smith a hand in testing yesterday when he was asked if he wanted to race the car, as Smith would be competing in the Formula 5000 Lady Wigram Trophy event in Christchurch instead.

He jumped at the opportunity, while in a separate development, it was confirmed that he would join the M2 Competition team for the NZGP.

Looking ahead to the Hampton Downs meeting, Bamber said getting a last-minute drive "always makes things interesting".

"The guys had two hours' practice yesterday so we're a little bit behind the eight ball on that," he said.

"I've driven the TRS quite a lot. We'll just take it as it comes and see what comes about, but I'm looking forward to getting back in a car and driving again."

Bamber, 20, has won 18 TRS races in his career, the second highest tally behind Daniel Gaunt's 20, and he has twice been series runner-up.

The former A1 GP driver also has an excellent record as a late call-up.

Last October, he went to China to commentate on Superleague Formula racing there.

He end up driving on two consecutive weekends, winning both meetings and picking up 100,000 euros ($175,000) each time.

Bamber was looking forward to resuming his battle with the 16-year-old Evans, who leads the series after taking out three of the six races during the rounds in Invercargill and Timaru last month.

"It would be nice to get in front, but it's not going to be easy," he said.

"We'll be working hard to make it happened, but we'll see how this weekend goes and use it as build up for the grand prix."