I cursed when I saw it. A police van parked at the side of the road, flashing intermittently as cars streamed past. A speed camera.

I had a good idea that I’d been snapped, but was I driving over the limit? Just a few moments previously, my youngest daughter had teased me for driving too slowly, calling me ‘tortoise’. I have always driven at low speeds, rarely going over 55mph, even on motorways. But on this stretch of road, in the dark, with driving rain, I have to admit I had no idea what the limit was – I guessed it was 40, so thought I’d be fine.

A few days later, I found out exactly what it was, when a letter arrived informing me I’d been driving at 40mph in a 30mph zone and inviting me to choose between penalty points and a fine or a speed awareness course, costing almost as much as the fine.

Like most people in this position, I chose the course. It was a revelation. If you passed your test as long ago as I did and think you still know your stuff, or have ever known it, you’re mistaken. It was as though the Highway Code were new to me, I’d forgotten so much. For instance, if I’d known that, unless otherwise indicated, street lamps always mean 30mph, I wouldn’t have been in that classroom. Time after time I’ve been confused when driving in the dark and failing to spot any road signs. Now, thanks to some valuable tips, I’ll have an idea as to what limits apply.

I didn’t know that closely spaced central white line indicate a more hazardous stretch of road, or that the position of your tyres when waiting to turn right could save your life if you’re bumped from behind. Keep them straight.

I’ve been driving, completely oblivious to such things, for more 35 years. Scary. Yet I wasn’t alone in my ignorance. The other people – mostly my age – filling the packed room, also had gaping gaps in their knowledge.

But I did know that a few extra miles per hour on the clock could make a big difference to the outcome in the event of an accident. We all knew that – yet still we exceeded the limit. Everyone does it – whether we are late for an appointment, rushing to get the kids to school, or just not concentrating.

As the course tutors said, it is far harder to keep to low speeds than to travel at higher ones.

So I’ve served my penance: four hours in a room with a bunch of strangers and an overhead projector being urged to take care and slow down. I know I will.