The North Atlantic Drift is a branch of the Gulf Stream that flows along the coast of Europe and directly affects the climate of the British Isles. The North Atlantic Drift brings warm, moist air from the tropics to the UK, which helps to create the country's mild, maritime climate. The North Atlantic Drift also influences the weather patterns in the UK, bringing with it mild, wet winters and cool, dry summers.
In summary, the Gulf Stream and the North Atlantic Drift are the two ocean currents that have the most significant influence on the climate of London and the UK. These ocean currents bring warm water and mild air from the tropics to the UK, which helps to create the country's mild, maritime climate.