Operafantomet: phantoming

The cast of mid-1988 in West End, after a charity event where royals were present. The cast was Dave Willetts, Claire Moore (Jan Hartley-Morris), Michael Ball, Maria Moll, Royce Mills, David Firth, Mary Millar, John Aron and Janet Devenish. 

Several has suggested it’s the July 1988 charity gala, but the original scanner of the photos labeled them “April 1988” and was sure of this dating. I know they had several charity events in 1988, including a “Children in Need” one in October, which resulted in something like 5 different souvenir brochures this year. So they might have had one in April as well; however I have not be able to find out which one. Is that Princess Anne in a stripy blue dress?