Seymour Tower is owned by the States of Jersey. The islet L'Avarizon on which it stands is about 2 kilometres out to sea from La Rocque Point, but such is the extreme rise and fall of the tide on Jersey's east coast that the tower is accessible across the sand and rocks at low tide, which has led to numerous people being cut off by the rising tide over the years and having to be rescued or losing their lives.
The tower was built in 1782 on a previous square foundation. It was either named after the then Governor of Jersey, Field Marshal Henry Seymour Conway who instigated its construction, or more likely Eduard Seymour, 1st Duke of Somerset who was Governor from 1537 to 1550, and who constructed a square tower on the same spot in 1540.
The new tower was armed with the usual musket loop-holes and 2 x 12pdrs mounted on the roof and originally manned by the Militia. In 1797 it had a garrison of twelve men of the Invalids, and in 1803 it was manned by ten men of the 3rd Royal Garrison Battalion.
As with the other military outposts it was necessary to communicate and the method used in the early 1800s was by candlelight. When there was a danger of an attack, lights were to be shown every half an hour. To do this cost 5.4 kg of candles a month. A report of 1840 stated that there were 2 x 24 pdrs on iron carriages on the battery. There was a magazine to hold 25 barrels of powder. There was no water tank.
The States bought the tower on 26 July 1922 for £60.
In February 1987 two riders and their horses, who became lost when a thick fog descended without warning, famously took refuge on the base of the tower itself and the horses could only be persuaded to come back down after a sand ramp had been constructed by excavators.
The tower was built the year after the French landed at La Rocque and although it has been suggested that it was named after the Governor, General Henry Seymour Conway, who initiated the construction of Jersey's coastal towers, it is more likely that it was named for Sir Edward Seymour, Governor in 1540 when an earlier tower was constructed at this location.
The tower was left alone by the Germans during their occupation of the island from 1940 to 1945. Perhaps they thought that it could serve no useful purpose as part of the network of defences they established throughout the island.
Along with all Jersey's other coastal towers and historic fortifications it is a listed building, described as follows in the Jersey Heritage Historic Environment Record website:
- "Seymour Tower is an exceptional example of Jersey's unique form of coastal defence tower, developed by Sir Henry Seymour Conway. It is one of 23 Conway towers built between 1778 and 1801 - the only one to have a square tower and one of only three to be constructed with an integral gun battery.
- "Shown on the Richmond Map of 1795.
- "Tower with gun battery at the base, built 1782 on an islet with historical associations dating back to the 6th century. The tower is square and built of regular squared and well-tooled blocks of granite with dressed granite around openings. The tower walls taper externally.
- "The tower is arranged on four levels. The entrance door is raised above head height (originally reached by removable ladder). There is a finely carved keystone - GR 1782 - above which is a window opening with original iron bars in situ. A pair of timber doors opens inward into a small well area, from which an opening shows through into the magazine store below. There is a step up into the entrance level.
- "The walls of the room are roughly squared granite with openings dressed with granite lintels and brick. There is a circuit of loopholes around the room designed for musketeers, above which are small windows. There is a fireplace in the southwest corner of the room, with an arched cast iron inset and mortar surround with late twentieth century graffiti.
- "There is an exposed joist timber ceiling that appears to be a later replacement, with the original main beam surviving (from which hang timber storage racks). Access to the upper level is via a modern timber companionway stair.
- "The room has a brick floor with thin mortar finish, set into which is a hatchway. The wooden hatch door appears to be early and was repaired using a plank from a German WWII box - marked 'Reichs' The hatchway provides access to magazine stores at lower basement level. Wooden steps from the hatchway lead down into a lobby area from which access is gained to a pair of magazine stores. The lobby has granite walls and a brick ceiling.
- "An original timber beam runs the length of this space (from which hangs an historic wrought iron lamp hook) At the east end of the lobby is an opening at head height, leading through to a well by the entrance doors into the tower. There is a pair of brick vaulted magazine stores. Both stores are lined with brick with a pair of baffled ventilation slots with offset ducts to the exterior of the tower.
- "The west magazine has a heavy timber door with full width iron strap hinges and sturdy iron bolt. There is an earthen floor. There are two sets of initials carved into the inside of the door frame. The east magazine has a heavy timber door with later bronze door fittings. There is a timber plank floor laid on sand. The upper level has walls of roughly squared granite with openings dressed with granite lintels and brick. There is a circuit of loopholes around the room designed for musketeers, above which are small windows. There is a fireplace in the northwest corner of the room - blocked with modern bricks. There is a wooden plank floor and exposed joist ceiling with a pair of iron beams supporting the roof platform.
- "Access to roof level is via a modern timber companionway stair. The stair up to the roof platform climbs into a small wooden cabin (now encased in fibreglass). The timbers of the cabin are covered with dates and the names of people who have visited the tower since the beginning of the 20th century. There is a granite parapet with mortar capping around the top of the tower.
- "In the north east corner is a taller loop-holed niche set into the width of the parapet, overlooking the battery below. In the southeast corner is a rendered chimney stack with a Fareham ware pot. In the southwest corner is a rendered chimney stack without a pot. Between the stacks is a modern enclosure covering a water tank.
- "On the east side of the base of the tower is a battery. The battery has a D-shaped plan, low encircling defensive wall of squared granite with dressed granite copings, and granite paving. The north wall of the battery continues alongside the tower to provide access to the tower entrance and steps down onto the rocky islet. A granite step at the entrance to the battery is carved with a North orientation line."
Seymour tower is now administered by Jersey Heritage and is available to let by up to seven people for £350 a night, including a guide. This is how it is described on the JH website:
- "Join your very own guide for a once-in-a-lifetime experience staying overnight, two miles offshore. Completely surrounded by sea twice a day, Seymour Tower offers a fantastic base for exploring Jersey's marine wilderness at low tide.
- "Accommodating up to seven people plus your guide, Seymour Tower offers a truly unique experience. Standing on a rocky outcrop off the south-east tip of Jersey's National Park in an internationally recognised RAMSAR wetlands site, the Tower offers guests the ultimate retreat away from the hustle and bustle of the main land. It’s perfect for anyone looking for adventure; use it as a base for low water fishing, guided walks at low tide or bird watching.
- "Each group staying at Seymour Tower has their own personal guide who stays with you throughout and arranges the best access times and will tell you about the unique flora and fauna whilst you trek across the mars-type landscape when the tide is low. During your stay you can watch the incoming tide from the parapet as it rushes through the surrounding gullies.
- "Built in 1792, the Tower has been well appointed to accommodate visiting guests. Spread over two floors with cooking facilities and wood burning stove on the ground floor and the bunk room on the upper floor with a basic chemical toilet. There are six bunks in the upper room for which we recommend you bring sleeping bags and pillows, with a separate room for your guide on the ground level.
- "While the facilities are basic, there is solar power for lighting and the fridge and gas for the cooker. Seymour Tower has no running water, but drinking water is provided along with logs for the wood burning stove. Guests are required to carry all their food, clothes and sleeping bags out to the Tower. In addition all waste (including bagged toilet waste) will need to be brought back and disposed of on shore."