Mirror – The Duchess of Cambridge was among the hosts at a Buckingham Palace garden party, stepping in for the Queen who pulled out of the sunny event. Kate was joined by Prince Edward, Sophie Wessex and the Queen’s cousin Princess Alexandra at the second garden party of the season this afternoon. However, her husband Prince William was unable to join the royal group as he had been in Staffordshire earlier today unveiling a new memorial for submariners at the National Memorial Arboretum…