The start of round 17 of the 1978 USAC Championship Car series, at Brands Hatch, on what became known as the Indy circuit. 16 US drivers came for a UK double header in October '78, featuring races at Silverstone and Brands, a week apart. AJ Foyt won at Silverstone, Rick Mears at Brands Hatch, but Danny Ongais was the fastest at both before retiring from both races. Tom Sneva (5th in shot below) would go on to win the title with 7 poles and 10 podiums, but no victories.
"Shortly after the start eventual winner Rick Mears leads in a Penske -Cosworth from Gordon Johncock (Wildcat-Drake), Danny Ongais (Parnelli-Cosworth), Bobby Unser (Lightning-Cosworth), Tom Sneva (Penske-Cosworth), Al Unser (Lola-Cosworth) and Tom Bagley (Watson-Offenhauser)"
1978 USAC Indy Trophy (Brands Hatch) by
John Millar, on Flickr
Edit: keep looking through this guy's Flickr, he's got some great colour photos from the '78 British GP at Brands too.