The Spice Girls said they were "excited, humbled and proud" to be at the musical inspired by their music Viva Forever!
The singers also praised the writer Jennifer Saunders as well as the cast of the musical.
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The comments are the latest twist in the row between the US and EU countries including Britain over trade tariffs.
St Paul’s Girls’ School in London was criticised by a former pupil over the exercise, which resulted in money going to charities.
‘They kept overtaking each other, so maybe the match will be closer than we expect,’ said Richard Nicholson, of Cannon Hall Farm, near Barns