Thruxton in Hampshire, the fastest track on the calendar, is the setting for the third event in the 2012 Porsche GT3 Cup Challenge GB with a pair of races on Sunday (17 June). With the cars topping 150mph, Thruxton is one of the most challenging tracks in Britain and Sunday marks the completion of the first half of the championship schedule.The Porsche GT3 Cup Challenge is managed by Porsche Cars GB alongside the Carrera Cup GB and is growing as the season develops, with steadily building competitor interest. The championship received championship status this year for the six-event, 12-race season and is for the cars from 2009 or before, including the 996-model cars from up to 2006.Heading the GT3 Cup Challenge GB entry will be the drivers who shared the race wins at Snetterton when the season opened at Easter. In two exciting races, James Birch (IN2 Racing) and Steven Liquorish (Team Parker Racing) took a win each and Birch then underlined his pace by scoring an excellent double win at Rockingham to make it three wins from four races and take top slot in the championship standings. With his first Porsche win under his belt after a polished performance at Snetterton, Liquorish will be a big threat, while other leading contenders include John Ferguson (ASK Racing) and Northampton-based racer Neil Houston (Team Parker Racing). Drivers set to have their first experience of the unique challenge of Thruxton include former British Rallycross champion Mark Flaherty (Redline Racing) and racing newcomer Guy Riall (Almara Racing), while another Thruxton debutee Mark Cowne (Kruger Cowne) heads the entry for the earlier cars in Class 2.With a 20-minute qualifying session and two 25-minute races in the space of just six hours during Sunday, the pressure will be on the teams and drivers in a day that could prove pivotal in the contest for the season-long championship.After qualifying at 11.10 on Sunday, round five will start at 14.10, with round six at 16.50. Both races will be filmed for transmission on the Porsche Origin website and Porsche’s YouTube channel.Current provisional championship points:Overall: 1 James Birch, 66; 2 Steven Liquorish, 61; 3 Neil Houston, 60; 4 Peter Smallwood, 57; 5 Justin Sherwood, 42; 6 Mark Cowne, 38; etc.Class 2: 1 Mark Cowne, 28; 2 Tom Hallissey, 11.