The Porsche Cup of 2002 had morphed into the Porsche Carrera Cup for 2003, which brought the series into line with the other Carrera Cups which existed in mainland Europe, Asia and support the Formula One Grand Prix. Initially for the opening round at Mondello Park, the grid didn't even make it into double figures, with the numbers being boosted by the two guest cars, one of which won both races, piloted by former Indy Lights racer Damien Faulkner.

For the second meeting at the London Champ Car Trophy event, title contender Barry Horne was joined by the man who would be his closest challenger for the championship, with ex-F3 driver Richard Westbrook making a full-time return to racing after several years doing bit part drives because of a lack of funds. Westbrook immediately had an impact at Brands Hatch, when his Team BCR car took both wins, while Horne was content to rack up podium finished after struggling with a poor setup choice in his Team Parker Racing machine. Horne fought back at Thruxton, when he won his first race of the season and Westbrook was disqualied from a win after a technical infringement. David Pinkney benefitted from that exclusion to pick up his what was also first win of the year. Thruxton also saw sixteen year old Jonathan Cocker come to prominence, when he shocked the establishment with a second place and showed more promise throughout the rest of the year in his Redline Racing entry. Horne and Westbrook took a win apiece at Silverstone and moved on to Rockingham in June, where Horne took victory in both races.

Porsche wheeled out one of it's big guns at Croft to add another element to the championship. German driver Mike Rockenfeller threatened to win the second race after starting at the back of the grid, but couldn't beat Westbrook who took both races, which helped his title chances immensely, when Horne failed to finish them. At Snetterton in the baking August heat, yet another works driver appeared in the shape of ex-UK Formula Ford driver Pat Long. The American succeeded where his colleague Rockenfeller had failed and took a double win, although as a non-points scoring driver, the twenty points for a win went to Barry Horne and David Cuff in the sprint race and feature race respectively. Richard Westbrook did a carbon copy of his May performance at Brands Hatch in late August and took his win tally to seven for the season.

Horne led the series into the penultimate meeting at Donington Park, where he won the sprint race and finished third in the feature, which was won by guest driver Tim Harvey, with Westbrook taking maximum points in second place. Westbrook's team claimed the entrant's title, but the main driver's championship was still up for grabs between himself and Horne as the circus headed to Oulton Park in Cheshire for the finale. Jason Templeman took the win his pace throughout the year had merited in the sprint race, with Horne taking second place. Westbrook battled into third after clashing the race winner and despite a last corner move to take the final podium spot, he had to concede defeat to Barry Horne, who claimed the inaugural Porsche Carrera Cup GB. Westbrook did take the feature race from Horne and 2002 Porsche Cup winner Mark Cole, which gave him his ninth win of the year, but it was scant consolation after being in the title hunt right down to the wire.