Steam carrots, potatoes and peas, each separately, until tender but still firm, usually about 5-8 minutes. Make sure to salt the water in the bottom of your steamer generously. Do not let the vegetables overcook. As each vegetable is done, put it in a colander to drain and cool. Taste the vegetables for seasoning and sprinkle with a bit of salt if you think they need it.

Add all the vegetables to a large mixing bowl. Add the mayo and fold it into the vegetables until each bit is well covered. Add more mayo if it seems a bit dry, but take care not to 'drown' them.

Line a mold just large enough to contain your salad with clear plastic wrap (cling film) and then add the salad, pressing it down into the mold so as not to leave any holes. Close up the top with any wrap hanging from the rim of the mold. Place the mold in the fridge for a couple of hours (or more) to firm up. (This will allow the salad to hold its shape.)

To serve, unmold the salad onto a platter.