I'm on the train!

I'm always up for something new, and this is it. I'm writing this on a train.

It's the National Express 1205 service from Leeds to London King's Cross. We have just left Doncaster and the next stop is Retford.

I'm on my way to the British Library to do more Sherlock snooping. This time I'll be reading letters that Sir Arthur Conan Doyle wrote to his mother in Masongill.

Will it hold any clues? Elementary, my dear reader, elementary.