On stage, digital technology gave the 3,000-strong audience at the Abba arena in east London perfectly recreated youthful versions of Agnetha, Benny, Björn and Anni-Frid.
At the rear of the purpose-built auditorium, three of the legendary group, now in their 70s, appeared in real life, waving like the pop royalty they are. The crowd was in ecstatic meltdown.
