The RSC’s contribution to the Arthur Miller centenary celebrations is a new Death of a Salesman, so attractively cast – with Sir Antony Sher and Harriet Walter in the lead roles – that a transfer to London (Noël Coward Theatre, 9 May-18 July) has already been announced.Sher is Willy Loman, the title character whose once profitable selling has declined due to his own and his nation’s depression and, as Sher vividly shows, because his increasing desperation unsettles customers. His wife, Linda, faced first with the loss of a regular salary and then of any income at all is, as Walter’s performance makes clear, the stronger and more resourceful of the couple but trapped in an era when her designated role is to keep her man going to work rather than going her