Recently I was at a central London terminal station and wished to buy a ticket from my local station (which is a National Rail station in the London zones) to Nottingham with my TOCNE priv. On requesting my ticket from the sales clerk, I was questioned who I worked for. I stated my employer (which is also printed on the priv) and the sales clerk correctly identified that I could travel for free from my local station to central London because of an inter TOC agreement. I stated that I wished to pay the fare from my local station however as this would make it a cross London fare and include travel on the tube. On saying this the sales clerk told me I shouldn't have mentioned that and now he would only sell me a London Terminals to Nottingham ticket and if I wanted a fare from my local station I would have to buy it there. I would just like to question whether the clerk was within his rights to refuse to tell me a ticket I requested. Am I doing something against the rules by buying a ticket for a portion of a journey I am entitled to travel for free just to get a discount on the tube fare? I am wondering whether to put in a complaint but this might cause further difficulty in future if I encounter the same individual at a ticket office. Would like your views on this situation please. I can elaborate further if necessary.