I will soon have a 20'x 30' garden, with a brick wall along one border and wooden fences on the other side and back borders. Now nothing but lawn. As I have two small children, I want to keep some area for them to play in while still planting a kitchen garden.

So I was thinking of putting in a raised bed along some significant portion of the brick side wall, say 2-3' wide, 2-3' high (to avoid the kids stepping/falling into it) also made from brick (the house is also brick). Would plant mostly veggies with some interspersed flowers. I have been reading extensively in this forum, but haven't yet managed to find anything that quite covers this situation.

In London, clay soil, not too much freeze, what sort of footing would this wall need? Will the existing side brick wall need to be reinforced somehow? Would one straight raised bed be better or would some sort of zig-zig in periodically be stronger? Do I need to put gravel under the soil to be added to the bed for drainage? Anything else I'm not thinking of?

Comments much appreciated.