Pedestrians prohibited

TR218

Where: At the beginning of and at entrances to any carriageway, lane or path.
Purpose: To prohibit pedestrians from proceeding past this sign where they could cause a danger to themselves and to vehicles.
Action: Despite the fact that pedestrians are prohibited on such a road, you must still look out for them. Pedestrians may not enter or cross a road where this sign is displayed.

Manual on Road Traffic Signs, page 14.