if figures must remain on the game board, at a right hand bend where two monsters are blocking the corridor can a hero go past them, in effect leaving the board, can the hero H move to position 1 in 1 movement Diagonally

That move is legal, but it does not involve leaving the game board. Diagonal spaces are adjacent; there are no spaces between them, so nothing in another space can block the path between them.

Thanks for the reply, thats the way we took it, but just wanted to be sure.