The Bookmaker wants to check my identity means and written proof, is it normal ?

The Bookmaker wants to check my identity means and written proof, is it normal ?

yes, it is
It is a safety measure
Some Bookmakers have been cheated by fraudulent use of credits cards
A written proof is also useful in order to check you are an adult ; so that minors will not be able to bet
Some Bookmakers will not transfer your winnings to your bank account without these formalities.