Double bend

The double bend sign warns of two bends ahead, the first to the left, or to the right if the symbol is reversed. Slow down before the first bend, keep to your side of the road and do not overtake until you can see the road is clear beyond both bends.

Official Highway Code caption: “Double bend first to left (symbol may be reversed).”

Listed under “Mostly triangular” in The Highway Code: traffic signs (GOV.UK). For every sign in more detail, see the Department for Transport’s Know your traffic signs.