The 56-year old Branson, who was knighted by Queen Elizabeth in 1999, said he was inspired by former vice president Al Gore to make the commitment.

• 56岁的布兰森在1999年时，受伊丽莎白女王册封为爵士，他表示是受了前美国副总统高尔的启发，而做了这项承诺。