On all BA flights the following weight tlimits for hand / luggage

Class of travel Piece allowance & dimensions Weight allowance

FIRST, Club World, Club Europe 1 Medium bag plus a briefcase or laptop Total weight 18kg (40lbs)

World Traveller Plus - 1 Medium bag plus a briefcase or laptop - Total - 12kg (26lbs)

World Traveller, Euro Traveller, UK Domestic- 1 Medium bag 6kg (13lbs) total 6kg (13lbs)

Children (paying 50% of adult fare) Same as adult allowance Same as adult allowance

This is enforced in the UK at most aiprots but outstations tend not to adhere to it, which causes arguements in the Uk when transit passengers arrive with massive loads of hand luggage

Hand luggage is meant to be for something that you need in the cabin for your flight.
Infants 1 Medium bag 6kg (13lbs) total weight 6kg (13lbs) on all flights