Hello Luckyjo, and welcome to Rootschat

The best way to remove the biro is to let our restorers have a go at removing it digitally. I am a photograph conservator by profession and I would think at least twice about trying to remove the actual biro from the physical photograph...it would be very difficult and possibly not very successful.
Don't worry, the Rootschat restoration experts will no doubt be along shortly and you will have plenty of restored images to choose from

Cheers
Prue