Osbornes HHW933D, Bristol VRL / ECW. The prototype VRL with chassis number VRX-2, exhibited at 1966 Commercial Motor Show, then used as a demonstrator, to Bristol in 1970 and to Osbornes in September 1973.
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Seen here on Ipswich Transport Society's Ipswich to Felixstowe rally.

Photo taken by Eric Thompson, May 1974, Felixstowe