By Antony Clements-Thrower Brothers-at-war William and Harry are set to reunite to honour their beloved mother tomorrow night – from thousands of miles away. The Prince of Wales is expected at the Diana Legacy Awards ceremony, introduced in 2017 to celebrate the life of the princess on the 20th anniversary of her death. The heir will attend at the Science Museum in person where he will give a speech. Winners of the awards, handed out to people aged between nine and 25 who improve others’ lives, will also get to meet his brother – albeit virtually as he will still be in his Californian home. La…