Prince Philip is famously required to walk two steps behind his wife in public.

But is he required to stand two steps behind her, even when this leads to his head and that of his wife's being on different sides of a theatrical curtain?

That's what happened when the couple stood as they listened to the National Anthem today in Salisbury. The Queen and Duke of Edinburgh are visiting the South West of England as part of their Diamond Jubilee Tour of the country.