The tremendously close racing generated by the Silverstone National circuit is next on the schedule for the Porsche Carrera Cup GB with rounds 13 and 14 at the Northamptonshire circuit (21/22 August).With ten wins from 12 races to date and a 40-point championship lead, it's going to take a disastrous weekend to derail Tim Harvey in his bid to win a second Porsche Carrera Cup GB title. Now, Oxford-based Harvey will race on his home track of Silverstone.Last time out at Snetterton, Harvey (Red Line Racing) shared the wins with Michael Caine (Motorbase Performance) and it is Caine who continues to be the big threat to Harvey. With 44 points available each weekend, this title race is certainly not over yet."Whenever you are doing well, motorsport is always about to bring you down a peg or two," warns Harvey. "So every race we've gone to, I've expected it to end and for someone to come out and thrash me, but it hasn’t happened yet. Every time we do it, the finishing line in terms of winning the championship, gets closer."As well as Caine, Harvey faces plenty of opposition. Stephen Jelley, Euan Hankey and Glynn Geddie – all from Team Parker Racing – are chasing hard. Meanwhile, Banbury-based Michael Meadows (Red Line Racing) is joining fellow Carrera Cup Scholarship winner Hankey as a strong podium contender, having qualified and finished fourth at Snetterton. Jelley was the closest rival to Harvey and Caine at Snetterton and will surely be a race winner before the season is over.In the pro-am1 category, Ollie Jackson (Addison Lee Motorbase) extended his lead over Jonas Gelzinis (Juta Racing) from Lithuania to 19 points with a double victory at Snetterton. Other leading pro-am1 contenders include Tony Gilham (Collins ReDesign Racing) and Ahmad Al Harthy and Archie Hamilton from Red Line Racing. Swedish racer Martin Ohlin (JHR) adds to the pro-am1 mix for Silverstone.In the battle for pro-am2, for the older cars, Milton Keynes-based Glenn McMenamin (Red Line Racing) overtook Mark Hazell (JHR) at the head of the points with a fine weekend at Snetterton, taking a win and a second place. Meanwhile, George Brewster (Celtic Speed), George Richardson (Motorbase Performance) and Snetterton race two winner Paul Mace (GT Marques) are all leading contenders and it is teenager Richardson who is gaining pace with every race weekend in his debut season at this level.With a superb 26-car field and the prospects of three battles within each race, it is going to be another great weekend for the Porsche Carrera Cup GB.Carrera Cup qualifying is on Saturday at 11.55, with the first race at 12.25 on Sunday and the second race at 16.25. Both races are due to be shown live on ITV4 in the extensive BTCC race day programme, which starts at 11.30am