Unless you couldn't physically have made the outward journey before you are departing. Then you'd be in trouble.
Hi,
Is there anything to stop you using a return portion of a ticket first? In this instance, the ticket is almost £15 cheaper buying it from my destination to my origin.
Would be travellin with Virgin - would they get the hump?
I don't think the asking to see the RTN portion is enforceable, and in any case that only arises on your return journey when you are using the outward portion and it is, by then, less suspicious.
On your outward journey you are using the return portion and they can't moan about the outward then.
There is a journey I regularly do using this method which saves approx 50% of the ticket price!
Guards can and regularly do ask to see an unstamped return portions (especially with high value tickets like Anytime Returns), if you do fail to produce this you could be charged the FULL open fare or if you are in a penalty fare zone you could recieve a penalty fare.
Regularly? I don't think this has ever happened to me.