Thanks for your reply Wriggler7.
I was traveling from Kings Cross back to Harpenden after attending a job interview when the inspector requested a ticket so I presented him with the travel card. He then requested the photo ID card that accompanied the ticket to which I replied that the ticket was not mine and was unaware that the ticket had to be accompanied by the ID card. I offered the pay the fare and fine at that moment in time but was told because I had present a ticket that was not mine it would be reported.
Obviously he retained the ticket and having been paying my sister in law's train fare since.
Let me know if you need anymore details.