We were told he used to caddy as a kid really early on in the first series, yet it took several series before AC12 worked out it was him.
I’m pretty sure that he didn’t mention being a caddy until he was talking to Hilton in the penultimate episode of S1. So it wasn’t long before he was revealed to be the caddy properly.
As for Buckells, I’ve been saying for ages now that he’s my lead suspect.
It would be really unsatisfying if Jed made the big bad someone we don’t know, or who’s only come into it near the end. It’s also hard to conceal if it’s someone we know well, as everyone is examining everything. Buckells would be the ideal candidate as most won’t suspect him as he’s so inept.
Buckells has been hiding in plain sight all along - and he does just keep coming back doesn’t he, even though there’s no real narrative purpose most of the time. And he was the one who was given the Laverty case by Hilton in S1.
I wish I’d put a bet on when this idea first came to me in S4. To paraphrase Dwight Schrute, he is the person I most medium suspect 😬