Before the M6 was completed the way to travel southwards on the West Coast of the
UK was to head for Liverpool docks, go through the Mersey Tunnel and
follow the A41 for Chester and points south. It was not a quick process.
Because the Mersey Tunnel was such a potential bottleneck they had to
have a robust strategy for dealing with accidents and breakdowns - it
was a fleet of specially adapted Land Rovers with tools and recovery
equipment aboard. I was there, I remember, I saw them. However they were
not red and they did not look quite like this, but they were Series 1 SWB models (86" or 88") with tool chests built into the back body.
I can't find pictures on the Internet, nor can I remember what colour they actually were or any more than that - just a trip to Chester Zoo in about 1960 when I was familiar with the Dinky Toy and was very struck by the difference between the toy and the real vehicle when passing through the tunnel.
Update 30th June 2020 - A very kind user of the Little Wheels museum has sent me a photo of the tunnel, just as I remember it - and there is a red Land-Rover, they must have been off duty when I was there.