The weekend of 6/7 October marks the biggest date so far in the history of the Porsche GT3 Cup Challenge GB as the final two rounds of the season put the drivers in action on the BTCC-supporting programme at Silverstone.The GT3 Cup Challenge GB is managed by Porsche Cars GB alongside the Carrera Cup GB and has grown steadily across the season. The six-event, 12-race championship is for the Carrera Cup cars from 2009 or before, including the 996-model cars from up to 2006.Now, for the final two races, the championship steps up to join the Carrera Cup on the BTCC support programme and, with the overall title to be decided by Sunday morning, it promises to be a fitting finale to the season.Heading the entry into the final two rounds is championship leader James Birch (GT Marques), who has enjoyed a stunning season with five wins, three seconds and a third from 10 races to date. The Buckinghamshire racer heads to Silverstone with a 22-point lead and two more podiums would be enough to claim the title.  Im really looking forward to the weekend and, touch wood, wrapping up the championship, said the former single-seater racer. I just need to finish and beat Steve, he added.The Steve that Birch needs to be beat is Steven Liquorish (Team Parker Racing), who has claimed six podiums during a cracking season to be the only driver now in a position to come between Birch and the title. Anything can happen yet in the last two races, said Liquorish. Its going to be very tight on the National circuit. With three wins from the last four races, Justin Sherwood (Team Parker Racing) is the man on top form right now. The former F3 racer missed a couple of races earlier in the season so is not in the overall title race, but is more than capable of winning again, while John Ferguson (ASK Racing) and local racer Peter Smallwood (Parr Motorsport) are both podium contenders.Running fourth overall in a remarkable debut season of racing is Mark Cowne (Parr Motorsport), while new to the grid for Silverstone will be young Harry Whale (IN2Racing) and Nick Staveley (sibsport performance). Harry, the son of experienced all-rounder Nick, is showing great form at this early stage of his racing career, while Staveley makes a welcome return to racing after a five-year sabbatical.After qualifying at 09.00 on Saturday, round 11 will start at 17.35, with round 12 at 10.25 on Sunday. Coverage of round 12 will be shown during the live BTCC programme on ITV4, which runs from 11am to 6pm.Current provisional championship points:Overall: 1 James Birch, 183; 2 Steven Liquorish, 161; 3 Justin Sherwood, 107; 4 Mark Cowne, 99; 5 John Ferguson, 93; 6 Peter Smallwood, 79; etc.Class 2: 1 Tom Hallissey, 32; 2 Mark Cowne, 28.