Although heading E from London is not an obvious way to get to Santiago, pilgrims will undoubtedly have gone to the Kent ports, as they are the shortest sea-crossing. The popularity of this route will have been increased by the fact that it also passes through Canterbury, not only the seat of the Archbishop, but after 1170 the shrine of Thomas à Beckett. Pilgrims will also have crossed the river from Essex into Kent, though the only modern ferry is that from Tilbury to Gravesend. Many ports would have been available in medieval times, but nowadays the only one is Dover.
Because of Chaucer, the road from London to Canterbury is by far the most famous pilgrimage route in Britain. Although Chaucer does not give many details of the route or places passed through, it's clear it simply follows Watling St, the main A2 (and its modern derivatives). As this is a very busy road, this is problematic for the modern walker. It crosses the river Darent at Dartford ('Darent Ford'), where the church tower retains Saxon and Norman elements; there are also remains of the wall of the Augustinian, later Dominican, nunnery in Priory Road. Nothing remains of the 2 small chapels founded for pilgrims. Besides Rochester, where the Norman Benedictine abbey (now the cathedral) developed a cult of William of Perth, and of course Canterbury itself, there was an important Cluniac abbey at Faversham, though little remains of it. More remains of nearby Benedictine Davington Priory, where the church nave is now used as the parish church, and part of the cloisters were converted into a house. Also nearby is Ospringe, where Maison Dieu is an unusually well-preserved pilgrim's hostel. There were several wells dedicated to St Thomas en route: Chaucer mentions the curiously named St Thomas a Watering in Walworth, now marked by the Thomas à Becket pub on the edge of Burgess Park; there was a St Thomas Well at Singlewell S of Gravesend; and the Becket spring at Bapchild near Sittingbourne can still be seen.
The other major road to Canterbury was the ancient track, probably of Neolithic origin, from the Wiltshire Downs and Winchester along the N Downs to Canterbury and Dover, now called the Pilgrims Way. Besides pilgrims, this road will also have been used in medieval times by merchants taking wool from the sheepfarms of the Cotswolds to the Kent ports and markets across the Channel, particularly in Flanders. It was later also used by drovers to the big cattle market at Maidstone. The modern waymarked route from Winchester, which roughly follows this, is composed of two parts:
- Winchester-Farnham: St Swithun's Way
- Farnham-Canterbury-Dover: North Downs Way. Between Canterbury and Dover, the more direct suggested route for the Via Francigena can be used; see mapping on AVF site
From Rochester, this route can also be used by walkers from London. Here's a suggested route from London to Rochester, avoiding the main roads.
Chaucer, of course, had his pilgrims start from an inn. Those of a more religious bent might prefer to start from a church. There was a cult of Edward the Confessor in Westminster Abbey, the richest of all England's Benedictine abbeys and left unscathed at the Reformation because of its links with the Crown. There was also a Holy Rood cult in St Paul's, which also had a statue of the Virgin which ended up in Mondoñedo in Galicia, where it continues to be venerated as La Inglesa. There are also a surprising number of other monastic buildings which survived the Reformation, the Great Fire of 1666, and bomb damage in World War II. The Augustinian priory of St Bartholomew's Smithfield is probably the finest Romanesque architecture left in London. The Temple church with its circular nave, HQ of the Templars, and St John's Clerkenwell, HQ of the Knights Hospitaller, were both C12 in origin. St Helen's Bishopsgate was originally a Benedictine nunnery. The chapter house of London's Charterhouse survives as a chapel, and the E part of the Augustinian priory of St Mary Overy was incorporated in Southwark cathedral. Little survives, however, of the Cluniac abbey at Bermondsey.
Despite all these remains, I would suggest starting at the City church of St James, Garlickhythe. Medieval in origin, along with most other churches in the City it was rebuilt after the Great Fire. It is connected with trade on the river, and has a fine statue of St James recently restored on top of the clock above the street.
Assuming you don't want to walk along the main road for 30 miles, one possibility is to follow the Thames instead. Cross to the S bank, and the Thames Path takes you E to Greenwich. If you like, you can make a short detour to look at Abbey St in Bermondsey which marks the former Cluniac abbey; there is however nothing to see. The Thames Path Extension continues on to the mouth of the Darent at Erith. Alternatively, the Green Chain Walk, a route linking parks and other green spaces, can take you there via the remains of Augustinian Lesnes Abbey; it crosses Watling St in the Shooters Hill area.
There is more or less a river path that continues on to Gravesend, but: there is no crossing of the Darent below Crayford, it's not very attractive, and there is a massive building site at Swanscombe for the Channel Tunnel Rail Link. From Gravesend, you can either take the towpath of the old Thames and Medway Canal to Higham and then paths and lanes into Strood, where Temple Manor was a Templar house, and over the old Rochester bridge. Or follow the Saxon Shore Way out to Cooling where the church of St James (now Churches Conservation Trust) is generally taken as the site of the beginning of Dickens' Great Expectations and was used in David Lean's film version; the vestry is lined with shells. An even greater detour would be to St James in Grain, which has Roman tiling built into the walls, though it's probably best known for the Romanesque carving over the door.
Because of the problems of the Erith-Gravesend section, an inland alternative from Greenwich is to follow the Green Chain Walk to Chislehurst, and then the London Loop to North Cray, where the church of St James is of medieval origin, though the current building is largely C19. Then head E to Sutton-at-Hone, where a Commandery of the Knights Hospitaller, known as St John's Jerusalem, and an associated fishpond are now owned by the National Trust. Further E again, at Southfleet, Friary Court is a former monastic grange, and at Cobham the C14 College was originally a chantry; the medieval church has a fine collection of brasses. From here, head for the N Downs Way at Cuxton. You can either follow this over the Medway and then the Medway Valley Walk into Rochester, or continue into Strood.
S of Rochester, the Carmelite friary at Aylesford was the first in England and is now again a monastic community, with a shrine of Our Lady of the Assumption and St Simon Stock; they also offer accommodation. Further E, not much remains of the Cistercian abbey at Boxley where the Rood of Grace was famously exposed as a fake at the Reformation. Between here and Sittingbourne, in the village of Bicknor, the interior of the C12 church of St James has remained largely untouched since it was built; unusually, it is constructed of chalk ashlar. S of Faversham, Sheldwich also has a medieval church of St James.
In Canterbury, pilgrims had a wide range of shrines and religious foundations to visit. Besides the Benedictine cathedral housing the shrine of Thomas à Becket, there was the abbey of St Augustine, also Benedictine, the ruins of which are to the E of the city. Little remains of the Augustinian priory of St Gregory or the Benedictine nunnery, but the rectory and guesthouse survive of the Dominican friary. St Thomas's Hospital (see also here) housed pilgrims, and nearby is the chapel that is what's left of the Franciscan friary. A doorway in St George St is all that is left of the Austin friary.
Just before Dover, the church at Temple Ewell is a descendant of the Templar foundation. To the W, the chapel to the south of Wootton was a commandery of the Knights Hospitaller; and, to the S, various parts of St Radigund's Abbey, a Premonstratensian foundation sometimes called Bradsole Abbey, remain.
In Dover, Dover College occupies buildings that remain from the Benedictine priory, which housed both pilgrims from the Continent to Canterbury, and British pilgrims to the Continent. The Maison Dieu, now part of the Town Hall, also housed pilgrims. The originally Saxon church of St James was badly damaged in World War II. On W Heights are the ruins of a small Templar church.