Sent to me by my son who has solved it, and from this article in The Guardian this is The Miracle.
There is a single solution to the puzzle and whilst the usual Soduko rules apply, the following additional rules ‘help’ to crack it.
No two squares that are a knight’s move apart can have the same digit. (The knight’s move is 2 along and 1 to the side, as in chess.)
No two squares that touch either horizontally, vertically or diagonally can have the same digit. (As in, no two squares a chess king can move between in a single move.)
No two squares that are horizontally or vertically adjacent can have consecutive numbers.
Whilst it looks scary my son says it’s quite logical once you get your head around it. But he has a MUCH bigger brain than his father.
There’s more information in the linked article above - including some tips and if you want to you can find and watch a video of two clever blokes solving it - in 25 minutes.