However, in 1917 the British were severely short of men and Tull was experienced, a good leader of men and suitable officer material, so they broke the rules.
This rash of high-profile cover versions that are hitting the shops seems to indicate there has not been enough time to write some suitable, original material for these fresh performers.
One specific material he is working on may be suitable as a replacement technology for photovoltaic cells, one that promises to be one-hundredth of the cost of existing solar cells, which can overcome whatever efficiency loss it represents.