Terry takes her hand, explaining that Doreen is the name she prefers to her own. Doreen has multi-infarct dementia, a degenerative brain condition making her progressively incapable. Their hopes of happiness after retirement from work in the food industry were broken when Mrs Cahill's memory began to fail and dementia - which affects one in seven of those over 85 - was diagnosed.
Over the past five years she has become more and more dependent upon her husband. He now cooks, cleans and shops. He helps her wash and dress and makes sure she wears incontinence pads. He patiently sustains conversations that make no sense and he calms her confused anxieties. He provides round-the-clock care.
But Mr Cahill is 80 and while he looks fit, bright and a lot younger than his years, helpers say the last two years of his wife's severe decline have taken their toll. She is on a waiting list to go into residential care near their home in Greenford, west London. But Mr Cahill has been warned it may take years before a place becomes available and he does not know how much longer he will be able to cope. His greatest fear is that he will die or become too ill to help his wife.
For the moment he makes the most of Mrs Cahill's attendance at a day centre three days a week; a home help once a fortnight, for which he pays; a district nurse once a fortnight to help with bathing; and a sitting service once a week to allow him to attend a self-support group.
He admits he does not really know what care in the community will mean, but hopes it will ensure two weeks of respite care so he can have a break in the summer. 'I guess it will all come out with the wash,' he says.
Frances English, director of Alzheimer's Concern, Ealing, is not so optimistic: 'I think community care is a vicious joke on vulnerable disabled people and their carers. It raised expectations, but the reality is that the support, the residential and nursing home beds, are not there . . . Those that shout the loudest and know their way round the system may get the help they need. But the elderly, like Mr Cahill, rarely shout.'