I'm looking at going from Farringdon to Elstree & Borehamwood arriving at about 6pm on Thursday, and going back at about 10pm. I've not used Thameslink before, but it looks like the outward journey counts as off-peak if I buy a paper ticket but as peak if I use my Oyster? And that as a result buying a paper off-peak return with my 16-25 railcard is cheaper than the Oyster fare? I was also wondering if anyone could confirm that it'll be free for my father on his 60+ London Oyster - I did consult the appropriate map but I'm colourblind and can't quite make it out for certain Many thanks!!