Family killer sudoku competition

After the success of last year's family chess completion Micheal Howlett has challenged the family to solve killer sudoku problems quickly.

We will all try to solve a set of killer sudoko problems. The winner will be the person who solves a test selection of problems fastest. If we can't solve the all the test problems then the winner is the person who solves the greatest number of them.

Rules

• Don't look at the existing literature or code for solving sudoku/killer sudoku problems. We believe it is more interesting to figure out everything from scratch.
• Don't spy on other people's techniques.
• Don't copy other people's code.
• All solutions must be written in python.
• You must write a general solver capable of solving all killer sudoku problems.
• Specialising your solver for the problems provided is not allowed.