Chess Puzzle of the Week (142): Solution

Last week’s problem was composed by psychiatrist and geneticist Lionel Sharples Penrose, also a strong over the board player as well as a distinguished problemist. He was a member of a remarkable family. His children are Nobel Laureate in physics Sir Roger Penrose, who celebrated his 90th birthday yesterday, physicist Oliver Penrose, who was a strong chess player in his youth and still maintains an interest in chess problems, 10 time British Chess Champion Jonathan Penrose and geneticist Shirley Hodgson. Lionel’s brother Sir Roland Penrose, was a famous artist and friend of Picasso. Someone really ought to write a group biography of the Penroses.

This problem, which David Shire, in the July 2021 issue of The Problemist Supplement, describes as ‘one of the glories of British problemdom’ is a MUTATE: a type of problem very popular a century or so ago, and still attractive to practical players as well as problemists. The position is a complete block: White has a mating reply to every black move, but is unable to maintain the position, but can play a move which leads to CHANGED MATES: a black defence is met by a different mate from that in the SET PLAY.

The solution is 1. Kh5!, which unpins the white queen but, by unguarding f5, grants the black king a flight square: 1… Kxf5 2. Qf4#, a PIN MATE.

Now consider the g2 square, which is at the intersection of lines controlled by the rook on g1 and the bishop on h1. In the diagram, 1… Rg2 2. Bf3#, and 1… Bg2 Qxe3#. This is a GRIMSHAW: the move of either piece to g2 interferes with the other one. After the key, both mates have changed: 1. Kh5 Rg2 2. Qf3# and 1… Bg2 2. Qg4#: a CHANGED GRIMSHAW!

There are other changes as well. 1… Bf3+ is now met by 2. Qxf3# rather than Bxf3#. 1… Rxf1 is now met by Qg4# rather than Qxe3#. 1… e2 is now met by 2. Qxd3# rather than Nd2#.

We also have some mates which remain the same: 1… d2 is still met by 2. Bc2# and 1… Rxg3(+) is still met by 2. Nxg3#.

What an extraordinary construction!