On Friday I was travelling on an Advance ticket that involved a change of train at Clapham Junction. When I got to Clapham Junction I had 20 minutes between connections and I wanted to get through the ticket barrier (I'd come off the Southern service from Watford Junction - high platform number - down the stairs and turned right). I showed the ticket to the lady at the barrier and she had I had to get my booked train. I asked if I could go through the barrier to use station facilities and then get my booked train. She said no because I had an advance ticket I can't exit. I was very sleepy and jeg lagged, suffering from a cold, plus it was wet and cold and I couldn't be doing with the bother. I also didn't want any problems getting back onto the platforms. The lady appears to work for a security contractor rather then a train company (certainly not SWT, Southern/GTR or even LO. Had I been able to get out I might have gone to Lidl just by the station to get some affordable food but in the end I just waited until I got to my destination on the South Coast. Alternatively, I might have used station facilities the other side of the gateline. Is this wrong that I wasn't allowed out?