Bunch of grapes or bag of marbles

I don't follow the workings of the Church of England closely but twitter alerted me to this address by the Bishop of Sherborne supporting the Anglican Communion Covenant. here

I share it because the contrast between a bunch of grapes or a bag of marbles is new to me; and I like it. It resonates with our own baptist conversations in England. How do we relate together, what place does covenant have in this and what shape should those relationships have?

Drill down a bit and there are a whole load more questions to be asked about the nature of church, the place of local congregations and how they form part of the church catholic. But I think the bunch of grapes analogy has a lot going for it.