If you fly from London to Tokyo on BA and then from Tokyo to Beijing on a oneworld airline, then the answer is yes. Even if you have two separate tickets, BA policy is to through-check bags onto the second flight if that is another BA flight or a oneworld flight.

If you fly from London to Tokyo on BA and then from Tokyo to Beijing on a non-oneworld airline, then BA will not through-check the bags, and you will have to collect them in Tokyo and check them in again with your second airline.