Question: How many miles is the racing circuit in which Jack Dunfee played one of the "Bentley Boys" before the Second World War?

Context articles: Castle Combe Circuit
Dragon Racing
Davidstow Circuit
Roy Hesketh Circuit
Kyalami
Port Wakefield Circuit
Rufforth Circuit
Clive Dunfee
Brooklands
Jack Dunfee

Castle Combe Circuit is a motor racing circuit in Wiltshire, England, approximately 20 mi from Bristol.
 The circuit is based on the perimeter track of a former World War II airfield, and was opened for racing in 1950.
Dragon Racing (formerly Luczo-Dragon Racing) is an American auto racing team, involved in many areas of motorsport.
 The Dragon Racing team competed in the IndyCar Series from 2007 until 2014, and in 2014 Dragon Racing became one of the founding FIA Formula E teams.
 Dragon Racing was founded in 2007 by Jay Penske and Stephen J. Luczo.
 Dragon Racing is headquartered in Los Angeles, California, the largest EV (electrical vehicle) market in the world, and has additional operations in Great Britain at the Donington Park racing circuit.
Davidstow Circuit is a disused motor racing circuit and airfield built in Cornwall, in the United Kingdom.
 The circuit was built on the site of a World War II RAF Coastal Command base, RAF Davidstow Moor, opened in 1942.
 Davidstow circuit opened in 1952, and held three Formula 1 races between 1954 and 1955.
 The circuit hosted its last race in 1955, and was one of many of Britain's airfields to be transformed into motor racing venues.
 Davidstow circuit is notable for the first victory in a Formula One race by a Lotus.
The Roy Hesketh Circuit was a racing circuit located on the outskirts of Pietermaritzburg in KwaZulu-Natal.
 It was named after South African racing driver Roy Hesketh, who died in the Second World War.
 Doug Aldridge, Colin Dove, Ossie Fisher, George Finch and George Shrives got together as a Consortium from Pietermaritzburg in the early nineteen fifties to first build and then maintain and improve the circuit.
Kyalami Racing Circuit (from "Khaya lami", "My home" in Zulu) is a motor racing circuit located in Midrand, Gauteng province, South Africa.
 The circuit has been used for Grand Prix and Formula One races and has hosted the South African Grand Prix many times.
 Among the Formula One races held at the track the 1977 South African Grand Prix stands out, as it is principally remembered for the fatal accident that claimed the lives of race marshal Frederick Jansen van Vuuren and driver Tom Pryce.
 In recent years, the area surrounding the circuit has developed into a residential and commercial suburb of Johannesburg.
 More recently, Kyalami has played host to five rounds of the Superbike World Championship from 1998 to 2002 and later in 2009 and 2010, the season finale of the Superstars Series in 2009 and 2010, and the South African round of the 2008–09 A1 Grand Prix season.
Port Wakefield Circuit was a motor racing circuit located approximately 1 km east of the town of Port Wakefield in South Australia.
 It was the first purpose built motor racing facility built in Australia after World War II, and only the second in Australian history.
 The circuit was created out of necessity in 1953 when two years prior the South Australian state government banned motor racing on public roads, a ban that would stay in place until 1985 when it was rescinded to create the Adelaide Street Circuit for use in the Australian Grand Prix which had become a round of the Formula One World Championship.
Rufforth Circuit is a disused motor racing circuit built on an airfield in North Yorkshire, England.
 Rufforth circuit was built on the site of a World War II bomber base, RAF Rufforth, opened in 1942.
 The airfield remained in active service after the war, eventually closing in 1954.
 Rufforth circuit opened in 1959, and held races until 1962.
 The circuit hosted Formula 2 and Formula Junior races between 1961-1978 as well as numerous sports car events.
 The circuit was one of many of Britain's airfields to be transformed into motor racing venues.
Beresford Clive Dunfee (1904 – 24 September 1932) was a British racing driver, one of the "Bentley Boys" of the 1930s, who was killed in a dramatic accident at Brooklands
Brooklands was a 2.75 mi motor racing circuit and aerodrome built near Weybridge in Surrey, England, United Kingdom.
 It opened in 1907 and was the world's first purpose-built motor racing circuit as well as one of Britain's first airfields, which also became Britain's largest aircraft manufacturing centre by 1918, producing military aircraft such as the Wellington and civil airliners like the VC-10.
Jack Lawson Dunfee (26 October 1901 – 13 September 1975) was a British motor racing driver, theatrical impresario, and later farmer who was one of the "Bentley Boys" at Brooklands before the Second World War.