I read it more that a single would be half a current return fair, not that you need to buy 2 current priced singles, so you wouldn't need to buy a "return" single, just get another single on the way back, whether that's later in the day or another day, or ideally just whack a card at a barrier on your way in and out, at least for on the day bought tickets. It all sounds good in principle but it'll get fucked up somewhere and cost more.
I read it more that a single would be half a current return fair, not that you need to buy 2 current priced singles, so you wouldn't need to buy a "return" single, just get another single on the way back, whether that's later in the day or another day, or ideally just whack a card at a barrier on your way in and out, at least for on the day bought tickets. It all sounds good in principle but it'll get fucked up somewhere and cost more.