Llanddwyn Island lies on the south west corner of Anglesey, close to the village of Newborough. Although in the past it was an island, it is now so only at the highest tides, It was at one time connected to the mainland by a stione built causeway, today it is possible to walk across a sand bar that has gradually formed to link it to Newborough beach. In summer months there is a constant stream of visitors to the island which seems to be leading to ever increasing measures to create paths and fences to direct walkers, and reduce erosion.
The island is the site of a church established by St Dwyn, more commonly known as Dwynwen (holy or blessed Dwyn). She was a sister to Ceinwen, commemorated nearby at Cerrigceinwen and Llangeinwen; and one of twenty four daughters of Brychan, king in Brecon. Her first church here was supposedly founded in the late fifth century.. St Dwynwen’s church was already virtually ruined by the seventeenth century, however small portions still remain, along with the traces of the monastery buildings. It is said that hoping to cash in on the benefits of the shrine a a Benedictine monastery was established on the island in the Middle Ages. No visible evidence of the monastery remains, and it is generally considered now that it never actually existed.
St Dwynwen is known throughout Wales as the patron saint of lovers, effectively a Welsh saint Valentine, and her wells and shrine have been visited constantly, even after the ruin of the church. The parish at Llanddwyn was at one time among the wealthiest in North Wales due largely to the offerings left by visitors to Dwynwen’s shrine, and from the fourteenth to the sixteenth centuries it was considered the richest prebend in the principality. Wax candles were kept constantly burning at Dwynwen’s shrine, possibly a golden image of St Dwynwen was displayed and here “A thousand broken hearts her power invoked”
The church was largely abandoned following the reformation and local residents removed and re-used wood, stone and lead from the building. The community that grew up around the church dispersed, and some houses were lost to the sea.
In the late eighteenth up until the early twentieth centuries, the island was inhabited again, as beacons were built and pilots housed to guide ships into St Georges Channel. The rocks off shore had historically been the cause of numerous wrecks on a then busy shipping route. At present the beacon, lighthouse and old lifeboat station remain, although unused. The pilot’s cottages have been converted into a small museum which reflects the life of Dwynwen and recreates that of the more recent inhabitants of the island.
Traditionally lovers would visit her well or shrine to divine the identity of future partners or to test whether existing love would last. According to accounts of her life, Dwynwen was loved by Maelon Dafrodill, whom she loved in return. However, he was said to have made inappropriate advances, which she rejected; and as a result he stormed off, spreading rumours and gossip to besmirch her reputation as he went. Heartbroken, Dwynwen swore that she would never love again and prayed to God to cure her of her love. God granted that in future she should never wish to be married, and also her wish that all other true hearted lovers should either obtain their desires or be cured of their passions. He also finally released Maelon at her request, whom he had temporarily frozen into a block of ice. Dwynwen then took the veil and founded her church on Llanddwyn Island.
Not only lovers resortedto the shrine, Dwynwen’s well also gained the reputation for curing aches, stitches and pleurisy. Her church also developed a reputation for the cure of farmer’s beasts. The following story is widely reported.
Around the year 1650 the ploughing oxen at Bodeon took fright when at work, ran over a steep cliff and perished in the sea. This occurred on St Mark’s Day and the farmer concluded that it was due punishment for working on the saint’s feast day. To prevent future accidents he decreed that this day should henceforward be kept as a holiday and that two wax candles should be burned on that day in the porch of Dwynwen’s church. This practice was maintained well into the eighteenth century, the owner of the farm and other local farmers paying to maintain the church porch for this purpose at a time when the remainder of the church was in ruins.
There are three wells of note in the immediate area, Crochan Llanddwyn on the mainland and,on the island itself, are found both Dwynwen’s own well and also Ffynnon y Sais.
Crochan Llanddwyn, Llanddwyn’s Cauldron, is a pool on the mainland, hidden in the Newborough forest a little way off the road that runs from the toll gate to the beach car park. It was to this pool that the youth of the area would come to predict the course of their love. Perhaps as her island shrine fell into ruin, devotions paid at the shrine were transferred to this well. Another widely reproduced account; this by William Williams of Llandegai who recorded many local customs in the early 1800s records that
There was a spring of clear water, now choked up by sand, at which an old woman from Newborough always attended and prognosticated the lovers’ success from the movements of some small eels which waved out of the sides of the well, on spreading the lovers’ handkerchief on the surface of the water. I remember an old woman saying that when she was a girl she consulted the woman at this well about her desting with respect to a husband, on spreading her handkerchief out popped an eel from the north side of the well and soon after another crawled out from the south side. Then the woman told her that her husband would be a stranger from the south part of Caernarvonshire. Soon after, it happened, that three brothers came from that part and settled in the area, one of whom made his addresses to her and in a little time married her. So much of the prophecy I remember. This couple was my father and mother. 
The pool is not currently clear, rather it was choked with pond weed on our visit and no eels were to be seen.
Ffynnon Dwynwen, Ffynnon Fair, Ffynnon Dafaden
Dwynwen’s Well is considered a little problematical. There are records of a well dedicated to St Dwynwen, also often called Ffynnon Fair (St Mary’s Well) on the island although its precise location has been open to dispute. Although Dwynwen’s well was certainly resorted to for its curative powers there also remains some confusion over whether the lovers’ ceremonies were performed at Crochan Llanddwyn as described above or at St Dwynwen’s Well on the island, though i believe the former to be the correct location. Some sources state that the well on the island it is now lost.
There is a well on the island clearly marked on most maps as Ffynnon Dafaden (wart well). It has been recorded that at some period in history this well was resorted to for the cure of warts, and numbers of corks with pins stuck into them, a part of the wart cure ritual, were to be found in the well.
It is more than probable that this well is that dedicated to St Dwynwen. It lies high on a cliff above the sea on the north side of the island, little more than about 50 yards from the church. The water cascades from the well over the rocks into the sea. On our most recent visit the pool was swarming with little tadpoles.
Dwynwen, who is remembered for the maxim “There is none so loveable as the cheerful”, has been the subject of numerous celebratory songs and poems over the centuries.
Dafydd ab Gwilyn (ca 1315-1350) commences:
Dwynwen, your beauty like the hoar-fros’s tears:
from your chancel with its blazing waxen candles
well does your golden image know
how to assuage the griefs of wretched men.
What a man so ever would keep vigil in your choir
(a holy, shining pilgrimage), (you with) Inded’s radiance,
there is no sickness nor heart’s sorrow
which he would carry with him thence from Llanddwyn. 
St Dwynwen’s Day is celebrated on January 25th.
Ffynnon y Sais
On the same side of the island, a little closer to the mainland is Ffynnon y Sais. This is a small fresh water spring that emerges from the shingle at the top of the beach and runs in a small stream across the beach towards the sea. I am unaware of any traditions or stories relating to the spring, it is relatively small, and probably just noted as a source of fresh water; however the bay in which it is located is called Trwyn Ffynnon y Sais
A final notable feature on the island, close to the path that leads onto the island is actually marked on the visitor’s display boards as an old well. This is the feature generally known as Merddin Cil. It is a narrow stone lined chamber that goes down to a depth of some ten feet. Its purpose is unknown, however there is no evidence of it ever having held water or having been a well
On a visit in September 2012 we noted that excavations had been taking place inside the church. The floor level had been taken down, exposing the footings of all the external walls. Turf had been cut back to show the circular external wall around the area. One of the remaining window arches has also been taken down for restoration. The site is apparently being restored and conserved, with interpretative material to be displayed on site. BBC News Item
– for more information on the work being carried out see comment below from Tim Morgan.
 William Williams Manuscripts, quoted by Baring-Gould and Fisher in Lives of the British Saints
 Selected Poems of Dafyyd Ap Gwilym. Translated by Rachel Bromwich Penguin Books 1985 Quoted at http://teifidancer-teifidancer.blogspot.co.uk/2011/01/prayer-to-st-dwynwen-daffyd-ap-gwilym.html
There is an interesting general blog that covers Newborough and Llanddwyn Island here