When we purchased the bag of grapes early in the morning at Borough Market — one of the oldest in London — I had no idea just how useful they’d turn out to be.

We hung them on the back of the stroller, a plastic bag of little green balls.

Spending a day with a baby — nearly a child, one and half years old — is an ongoing exercise in the triage and mitigation of meltdowns. This is the first time I’ve spent a day with a baby of this age. When they’re younger they’re just little larvae. But one and half is a human — almost but not quite speaking. Sometimes walking.

They have frightfully short memories and switch emotional contexts like psychopaths. I can’t count the number of times during the day little Jake shifted from the happiest to the saddest to the happiest creature all within a few seconds.

Take away anything the baby likes at some moment — being carried, walking, sitting in a stroller, eating a cookie, anything — and you can expect screaming and tears. The only way to keep that from happening is to distract it for long enough (Three seconds? Five?) so that the baby then forgets what it was sad about. Suddenly the new context (now sitting or walking or being held by another) is just fine.

These grapes were our great context switching mechanism. Anytime we needed to move Jake or change his state, anytime his eyes began to well up or the facial muscles started to sadnessalign — clearly a pattern of recognition embedded deep within us — we plucked a grape from the bundle on the stroller and held it out to him. Suddenly: great happiness.

Mouth full of grape you can do anything to the baby. Throw him around, put him in a sack, cut his hair. It’s a real-life videogame power-up (the iPad being the ultimate of such powerups). Pop a grape into his mouth and you have just enough time to do whatever it is that needs to be done and not lose your mind.

Such a moment arose in this cathedral, the name of which I do not know. For a brief second, it looked as if the baby would unleash ultimate screaming upon the silence of the church. But he didn’t. Before his full-on wind-up could complete, we had replaced his worldview with a single, smooshy little object: his favorite thing in the universe at that moment or any other moment in which he is made aware of their existence. We gave the little bugger a grape.