In a few weeks I need to travel from Didcot to an address on City Road, London, quite close to Old Street station. I've tried googling the best route and I'm getting a myriad of different journey options! Some suggest changing at Reading for an Elizabeth Line service; others recommend staying on until London Paddington, before transferring to the Underground. Old Street is on the Northern Line so, presumably, I would have to change at least twice from Didcot. What would be the best/quickest/most efficient route do you think?