Town defences: The Fosse

Mediaeval Tonbridge was a fortified town. The castle was its stronghold, but the whole of the small settlement outside the castle gates was protected against intruders by a substantial ditch-and-bank structure known today as the 'Fosse'. This encompassed the town on all sides, except where the river or its tributaries form a boundary. The route of the Fosse can be seen on the plan below.

The Fosse must originally have been an impressive structure. According to the National Monuments Record there was an earth bank or rampart, up to 10 metres wide and up to 4.5 metres high. Outside this there was a ditch about 6 metres wide and 2.5 metres deep, parts of which may have been filled directly from the river, while others collected rainwater or were dry. The total length was about 800 metres, which implies that some 25,000 tonnes of material would have been moved – all without machinery – during its construction.

Just when the Fosse was constructed is uncertain. It may have been in the mid-13th century at a time when the Castle was being strengthened and its moat dug, or it may have been earlier. In 1259 Henry III granted to Richard Earl of Gloucester a licence to close his town of 'Tonebrugg' with a wall and to crenellate it (with stone or wooden battlements). This could refer to constructing something from scratch, or to improving an existing ditch-and-bank structure. Either way, no evidence has ever been found for the existence of any stone or wooden fortification atop the rampart, or of any revetment – cladding of the rampart with a protective layer of stones or other material.

With the rampart in place, the only ways into or out of the town by road were from the north means of a bridge and gated entrance near where the Ivy House is today, by a similar eastern entrance near the present Port Reeve’s House in East Street, or over the Big Bridge. This arrangement would have facilitated the collection of tolls.

The route of the Fosse can still be traced today. In the Slade area, a public footpath between Stafford Road and the end of Fosse Road runs along what was originally the line of the ditch, while the remains of the rampart, much overgrown, form a noticeable bank alongside. In the east, an outward-facing scarp or mud-bank is a conspicuous feature in private gardens between Bordyke and East Street, and on the south side of East Street. The name Bor-dyke itself commemorates the ditch, now filled in, which ran parallel to the street along what is now the north edge of the Parish Church graveyard.

In 1886 the local architect and antiquarian James Wadmore published the remarkable drawing shown below. It gives a bird's-eye view of the Town and Castle of Tonbridge as Wadmore thought they might have appeared in the year 1260. The view is from the north. The castle appears to dominate the small town, which is completely enclosed within the Fosse (shown here apparently holding water throughout its length). The only building outside the ramparts is the Priory, in the far distance. As a religious house it perhaps did not need protection.  

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