From over a thousand observations of the asteroid Eros at its opposition in 1930/31, he calculated a value of 8″.790 for the solar parallax. The task, which took him ten years, was one of the most impressive calculational feats of the pre-computer era. Jones was appointed tenth Astronomer Royal in 1933. In this role he introduced improvements to the timekeeping system at Greenwich (and demonstrated that the rotational speed of the Earth is not constant) and instigated the Royal Observatory’s move to Herstmonceux, Sussex.