Don't worry about catching up. The first half of each episode is dedicated to making sure that anyone who has accidentally failed to listen for up to at least five years will be fully up to speed in no time at all. They achieve this with improbable dialogue such as "Tony, don't forget you've got that meeting with the ministry man that you fixed up on the telephone yesterday after we'd had a chat about it, just before we went to the hospital to see that new baby, your gorgeous grandson Henry, that Helen had two weeks ago, remember?"