Every year, more than nine million people come from countries all over the world to visit London.They go to the theatres and museums;they look at interesting old buildings,many of them hundreds of years old;they sit or walk in the beautiful parks, or have a drink in a pub.They go to Oxford Street to look at the shops, or to Harrods.Two million visitors go to the Tower ofLondon.A million more go to see St Paul's Cathedral. Yes, London is a big and beautiful city with lots to see and do. But how did it all begin . . .?