The Mercy [2018] – ★★1/2 There is a method in his madness. This is the way some were able to characterise Donald Crowhurst’s insane desire and, ultimately, attempt to finish a single-handed, non-stop round-the world trip or the Golden Glove (Yacht) Race sponsored by Sunday Times in 1968. Completely amateur, Crowhurst, nevertheless, entered the race,…