My old man said follow the van, and don’t dilly-dally on the way.” We are seated in a circle, singing. The woman next to me is lusty, her voice clear and her hands tapping out the rhythm; the man opposite in his wheelchair looks slightly dazed but he mouths the words. People who might not be able to speak can often find language when it is set to music. Memory floods back. I am at a residential care home in Carterton, near Witney, Oxfordshire, run by the charity MHA, where two-thirds of the 68 people who live here have dementia. “I dillied, I dallied, I dallied and I dillied,” we sing, smiling, nodding, all joining in except the woman in…