I did know at the time about declaring and paying, but I'd forgotten about it since then. Thanks for reminding me.
It would only have applied to a fairly small minority of drivers: those who have access to red diesel in the first place, so who work on a farm or know someone who does who can sell it to them.
I remember I was having to travel about 80 miles a day to/from work, as I'd started a new job and hadn't yet moved to my new house which was closer to my new job, and I was starting to get concerned about how I'd get to work if I couldn't find somewhere that still had fuel.
I was lucky in that I had about a 10-minute walk to my local station, and then two trains would get me to within a mile or so of work, with a bus to work if it was raining. It never came to it, but I remember having one anxious journey home, trying to decide whether it was better to go straight home on the motorway, or to take a longer, more stop-start journey on A roads where there might be garages that still had fuel.
It was interesting on the M4 how many cars were going a lot more slowly than normal to conserve fuel. I tried to keep down to 50 on my way home each day; going to work, I was in more of a hurry to be there on time and could never wake up early enough to allow for the extra 50-versus-70 time.