This fascinating story prompted me to do some further 'net sleuthing and came across the following, attributing the poem "The Happy Old Couple" to a "Lord Wharton":

http://books.google.com/books?id=_CUTAAAAIAAJ&pg=PA126&output=text#PA126

"The Lily - A Coloured Annual for 1831" (p. 126)

THE ORIGIN OF DARBY AND JOAN. BY THE AUTHOR OF "DAME REBECCA BERRY (Elizabeth Isabella SPENCE)"
Within three miles of Tadcaster, in the West Riding of Yorkshire, there is a beautiful village called Healaugh, remotely situated, but celebrated from being the place where lived, more than a century ago, a couple called " Darby and Joan," and whose humble dwelling is still to be seen there.

The way leading to this rural spot had, as I drove thither, all the charm of soft pastoral scenery: rich meadows, filled with sheep and cattle; green hedgerows, intermingled with a profusion of roses and woodbine, and every bank enamelled with fragrant flowers. It was the month of June, when all the redolence of summer regales the senses, and invigorates the spirits, in beholding the gaiety of nature, and every animated object happy, amidst the song of birds, and the joyous aspect of summer.

Healaugh consists of one long street, with low thatched cottages, and formerly had rows of tall trees before every door, with a bench beneath. The Church stands at one end, partially covered with ivy, and, from resting on a green bank, embowered in lime-trees, is a pleasing object on entering the village.

Even now this sequestered little spot looks the paradise of humble life; for, in Yorkshire, the eye is not pained in beholding that squalid poverty too often seen in remote parts of England.

The rustic bench still remains on which the faithful Darby and Joan were used to sit: he smoking his pipe and quaffing his ale; she, in all the garrulity of age, relating tales of days long passed away with recollected enjoyment, surrounded by their children's children, (at this time the cottage is inhabited by one of their descendants,) or listening to their hopes and fears respecting their future prospects in life, until they almost forgot they were quietly passing into that state where hope and fear have no longer existence.

On Sunday morning the old couple were constantly seen tottering together to church, supported by some of their children or grandchildren; thus proving themselves still linked together in their duties to their Maker, as well as in their worldly enjoyments. Happy, enviable state! where sympathy doubles every joy, and lessens every grief; where kindred spirits mingle together, be it either in the highest walk of life, or the humblest of its paths. Happiness beamed with perpetual sunshine on the cottage of Darby and Joan, which is justly illustrated in Lord Wharton's ballad called

THE HAPPY OLD COUPLE

Old Darby, with Joan by his side,
I've often regarded with wonder:
He is dropsical, she is sore eyed,
And yet they are never asunder.

Together they totter about,
Or sit in the sun at the door;
And, at night, when old Darby's pipe's out,
His Joan will not smoke one whiff more.

No beauty or wit they possess,
Their several failings to cover;
Then, what are the charms, can you guess,
That make them so fond of each other ?

'Tis the pleasing remembrance of youth—
The endearments which youth did bestow;
The thoughts of past pleasure and truth,
The best of all blessings below.

Those traces for ever will last,
Nor sickness nor age can remove;
For when youth and beauty are past,
And age brings the winter of love,

A frcndship insensibly grows,
By reviews of such raptures as these,
The current of fondness still flows,
Which deepest old age cannot freeze.

The happy old pair are buried in Healaugh churchyard. Thither I bent my steps to look at their grave. I found the sexton busily employed preparing the place appointed for all men; and, as the person who generally has all the village annals by heart, to him I went for the history of the singular personages in question.

The sexton appeared to have numbered more than three score years and ten. He was a remarkably hale and good-looking old man; though his face was deeply scarred with small-pox, and he had only one eye, I scarcely ever saw so shrewd a countenance. There was in this solitary eye an expression of facetious humor, and at the same time low cunning, which amused me extremely. He actually personified the grave- digger in Hamlet; for not only with the most careless indifference did he perform his part in this scene of mortality, but he was also a humorist, and jested, as with a significant look he related the history of" Darby and Joan," and pointed out the spot where a stone marked their grave to every passer by.

To time immemorial will this faithful old couple be remembered, and quoted as an example of conjugal felicity, by the designation of "a perfect Darby and Joan," —in those instances, alas! too rare, where man and wife pass not only the spring-time of life, but old age, never asunder, having made a contract with each other in youth, to bear with the infirmities of old age together.