My husband and I are going to be London for six days in June and would like to make a day trip to Cambridge on Tuesday June 18. My preference would be to be able to come back when we prefer but what I have found are advance tickets which require commitments to specific trains and anytime tickets which are quite expensive. Is there any other alternative that I have not seen? My understanding is anytime tickets allow you to travel before 9:30 am which we do not need to do. I just would prefer to not to have to decide how long to stay ahead of time, although not at any price. We will have Two Together cards.