Many thanks again for taking the time to reply so comprehensively. I will do as you suggest, in honesty I am keen to avoid any aggravation which is why I wondered if citing the exemption was just likely to antagonise / strengthen the resolve to prosecute.

Many thanks for the excellent response. This occurred at St Pancras station. Whilst there are photo booths at the station they are some distance away from the FCC area and access to the thameslink services. Both my photocard, the ticket and my driving license were photocopied before being returned to me. I appreciate that by the letter of the law I was in the wrong but feel that the laws when properly applied are to ensure tickets are not transferred between passengers etc resulting in revenue loss etc. I would hope in this case that common sense would prevail and once it was acknowledged (as had been by the guard) that I was not trying to evade paying etc no further action would be taken. Your final paragraph contains excellent information. Do you think I should refer to this when replying or simply state the facts as best as possible and should I receive a further notice cite this? Or is the next step a summons in which case this will be too late? Once again appreciate the excellent advice and guidance.

Last month my ticket failed to work in a ticket machine and so I approached a guard to let me through the barrier. I purchase a weekly travel card from the ticket machine each week and pay by debit card. The machine prompts you to enter a photo card number prior to paying. On this occasion whilst purchasing my ticket I did not have my photo card to hand and did not recall the number from the top of my head. Rather than key in a random number i opted to type my name in as the photo card number so that it would be readily apparent that the travel card was mine (even if it did not match my photo card). When stopped the guard asked to see my photo card which i duly produced. The number on my travel card obviously differed from the photo card as I am fortunately not called GH 8578 V. I explained the situation to the guard and subsequently produced the receipt which tied up with my debit card number and also my driving license which demonstrated that the number entered on the travel card was in fact my first name. The guard acknowledged that on reflection the travel card could only be mine unless by some miracle i had happened upon a travel card valid for my journey and who's photo card number by a miraculous coincidence happened to be my name. I was told that this was fine and that he had to fill in a form and that I just had to verify what he said and then i could be on my way. I was not placed under any caution. His statement said that the number on my travel card did not mach the photo card - I agreed that this was true and signed and with my ticket returned was allowed through the barrier to board the train. I subsequently received a notice of intention to prosecute from FCC stating that I was found to be entering a train for the purpose of travelling without a ticket entitling travel. To say I was shocked by this is a slight understatement. Surely if in the opinion of the guard the ticket did not entitle me to travel I should not have been given back my ticket and allowed through the barrier? I should have been asked to purchase a ticket which entitled me to travel and that would have been that? I would also suggest that whilst perhaps I was in the wrong to have a ticket which did not display my photo card number it should be obvious to all concerned that this was not an attempt to travel without paying. Further to this at this point I was not on a train and so would question the offence raised? Can anyone suggest a suitable response short of explaining the facts and circumstances above....? thanks in advance