Thanks for the heads-up John. Whilst I do have a Steam account (for a different non-Trainz title), mine is protected by Steam Guard, which I would recommend users of Steam set up for their protection, as it will send a code to your email if a new machine attempts to connect to your Steam account, which would need to be entered for the access to succeed. (P.S. To change this:
1. Right-click the Steam icon in the taskbar, then click Settings.
2. Click 'Manage Steam Guard Account Security'.
3. Make sure 'Keep my account protected by Steam Guard' is selected' - if you only use Steam, tick the box below this to de-authorise other systems that have attempted to login.
4. Click Next, then wait for Steam to process the request.
5. Once this is done, click Finish.
The next time an attempt to login is made, a code will be sent to your email, which must be entered in order to login - make sure your email address is correct.
Shane