T he stage setup before Rosalía’s first of two headline shows at the O2 Arena is the back of a huge canvas, bearing just her signature and the stamp of her 2025 album, Lux. You spend the impatient moments before the set begins wondering what’s on the other side – what the completed picture might look like. The Catalan artist spends much of Lux questioning this, too. I called it a masterpiece in my review last year and I stand by that, not least after watching her perform it in real time. Set to a tremendous sonic palette of orchestra, flamenco and traditional fado singers, and delivered in 13 different languages, these songs examine ideas of faith, God and sainthood, love and lust, materialism and sacrifice. It demands study but never feels like homework – although the 18,000 or so fans in attendance have clearly done theirs, as they sing along to lyrics in Spanish, French, Arabic and Italian.…