4-Bed Rotation System

In anticipation of preparing my allotment I've been looking into how the 4-Bed rotation system works. The idea is to have four beds and rotate the veg grown in them every year. The aim is to avoid a build-up of pests and diseases specific to certain vegetables.
Now the key is in the word rotation, rather than just swapping vegetable beds around, as this video from Gardener's World explains.

In a nutshell the order of rotation is:

1. Potatoes. Plant in well dug soil with lots of manure.
2. Legumes (peas, beans, etc). These will deposit nitrogen into the soil by storing it in their roots so make sure you leave the roots there at the end of the season.
3. Brassicas (broccoli, calabrese, cabbage, cauliflower, etc). These love the nitrogen that's been left by the legumes.
4. Root vegetables (carrots, parsnips, etc). These don't need huge amounts nutrients. Any excess will just go into the foliage and not increase the size of the root.

Onions and other alliums like leeks and garlic can go in with the legumes as they like the same kinds of conditions.

Each season you move the vegetables round in order, with the potatoes following the root vegetables after the ground has had a good dig and more manure.

Well that's the theory and it makes sense on paper. I wonder how it'll work in practice!

Some more information on 4-bed rotation is here.