Edwardian murder

Caroline Luard was shot near Ightham in Kent in 1908. Within weeks her husband, a respectable Major-General, committed suicide. Two years later John Nisbet, a colliery cashier, was robbed and murdered on a train in Northumberland. Police arrested a man called John Dickman, who was subsequently executed. The conviction, however, relied on circumstantial evidence. In 1950 C.H. Norman, who acted as official shorthand writer at Dickman's trial, claimed that Dickman was framed for Nisbet's murder. Is it conceivable that John Dickman was guilty of both murders? Or was he framed, and unjustly executed? These true crimes bear all the hallmarks of traditional English period murder: steam trains, revolvers, an isolated summerhouse, retired army officers, parlour maids, as well as murder and love.