This in from Peter Brown:
"Just thought I would let you know that the tickets for the Mamma Mia! 10th Anniversary show Monday 6th April have just gone on sale. You can get these from the box office – 0844 482 5115 or www.mamma-mia.com.
It is meant to be a special show and I have heard that there are lots of VIPs attending! (unfortunately no names yet)
Tickets for this special occasion are the same price as normal Mamma Mia! tickets and are selling very fast."
Thanks Peter! Thanks also to J_ase and Mark Hooper – Mark found tickets here.