Rule 130 of The Highway Code states
130
Areas of white diagonal stripes or chevrons painted on the road. These are to separate traffic lanes or to protect traffic turning right.
if the area is bordered by a broken white line, you should not enter the area unless it is necessary and you can see that it is safe to do so
if the area is marked with chevrons and bordered by solid white lines you MUST NOT enter it except in an emergency
[Laws MT(E&W)R regs 5, 9, 10 & 16, MT(S)R regs 4, 8, 9 & 14, RTA sect 36 & TSRGD 10(1)]