Commonly fails. No need to buy a complete valve just replace the O-ring and it will reseal.
5x Central Heating Room Thermostats & Immersion Timer Job Lot Drayton TimeGuard
10x Central Heating Bleed or Blank Cap Radiator Valve Replacement O-rings, Seals
Goodility Brass Radiator Key for Bleeding Radiators, 5mm Radiator Bleed Key UK, Pack of 2 Solid Radiator Air Vent Keys for Optimizing Central Heating Systems
Event Decor Shop Solid Brass 5mm Universal Radiator Bleed Key – Heavy-Duty Valve Key for Air Venting and Bleeding UK Radiators, Ideal Plumbing Tool for Central Heating Systems - Pack of 1
Radiator Key Set of 2 Bleed Valve Tool for Central Heating System Air Release +
5pcs 12 Inch Air Vent Radiator Bleed Valve for Central Heating Systems