Tom O'Brien was a horse racing enthusiast. British and Irish racing communities mourn his death at 39 after a diagnosis of cancer. The Racing Post called him a great person. O'Brien won races at the renowned racing event. The Guardian and 7NEWS reported his death after a courageous battle with cancer. At Bangor, a close friend called him a hero and a brilliant rider. Yahoo News Australia said O'Brien was the second jockey to die in a short span. Tributes continue in the world of horse racing.