Sometimes when I'm bored I dig through the forum looking for questions from 3 years ago that never got answered...
The silver F1 in that image is chassis #001. Two distinct features which prove this can be seen in a larger version of the picture I'll share below. The first is the circular door button cutout - later production cars used a U-shaped version that fed into the rear edge of the doors to allow your fingers better access to open them. The second are the door mirrors - you can see from the protruding base that these are the Citroen CX-sourced mirrors, and not the later versions borrowed from VW's parts bin.
Chassis #001 wasn't the only F1 to have these two features, but it would be the only silver F1 that would, barring XP3 which had different front marker lights than the car in this image, thus ruling it out.
Another thing we can be certain of is that the image does show Harrison's Rocket as the plate in the larger version matches the one seen in your Goodwood FOS video.
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Anyway, has anyone seen chassis #025 lately? I'm kind of sad we still don't have more/better images of Harrison's car.
>8^)
ER