His Wikipedia entry is here.
Hailstone painted royalty and other prominent Britons, though his portraits of Royals were for entities with which they were associated, and not the royal collection. Some of his portraits of senior military officers are in the Imperial War Museum collection, as he was a war artist sent as far as Burma.
Dempsey, later promoted to General, was one of the best British generals in World War 2.
Park and Air Chief Marshal Hugh Dowding were the key Royal Air Force commanders during the Battle of Britain. These portraits of Dempsey and Park are decent likenesses, but I find Hailstone's brushwork detracts from what they might have been.
Hailstone made many paintings of dock workers, merchant seamen and such during the early years of the war. This strikes me as a better painting than most of those above.
A pleasing oil sketch, though her forehead seems a bit off. Ditto her hairdo.
An example of his wartime non-portrait work.