Every summer for the past six years, Bayreuth has risen to its feet to acclaim an English Brünnhilde. Catherine Foster, from Nottingham, was the heroine of Frank Castorf’s anti-capitalist staging of Richard Wagner’s Ring cycle. The director was booed to the rafters, the singer hailed as saviour. Three perfectionist conductors, Kirill Petrenko, Marek Janowski and Christian Thielemann, insisted on her return each year.