Plans have been drawn up to stage an eight-team international 'festival of rugby' in London this autumn, with the Six Nations sides joined by South Africa and Japan.
With continuing uncertainty about the scheduled north versus south November Tests going ahead, officials are scrambling to prepare contingencies.
One of those being considered is a one-off event involving two pools of four leading countries, with the possibility of round-robin fixtures and a final taking place at Twickenham.
The possible Autumn tournament in London would also involve South Africa and Japan.