These notes taken from the rear of the photo identify the people involved
Left to right
Ernie Jarvis (Foreman)
Harry Cooper (brother of Jack)
This is one half of a pair of trucks - i do have a copy of the photo with both in so will dig that out but cant find the original at the moment.
Images have been scanned through glass as didn't want to damage the images, so a bit fuzzy
Wickham Type 11 Saloon Inspection car with Meadows petrol engine and reversible seats circa 1929