On the night of the summer solstice I made my way to Hermitage Moorings just east of London’s Tower Bridge. There were about a dozen other vessels in the harbour when I arrived, tugs and Thames Barges mainly, which had all been lovingly restored by a community of passionate enthusiasts. The historic boats made an impressive sight with the dark wooden masts of the barges and their folded heavy red sails silhouetted against the great Royal Palace behind.

I found IDEAAL moored alongside an immaculately refurbished Thames Sailing Barge, which now served as a permanent residence for a young couple and their dog. Skipping over the artfully arranged nets and ropes on the deck of the boat I hopped onto the 50-tonne Dutch barge which had originally been built in the 1920s as a sailing vessel to carry freight and had since been converted into a live-work studio by owner Ben Eastop.

Estuary by Rachel Lichtenstein

Estuary by Rachel Lichtenstein

As the light slowly faded on the longest day of the year I sat on deck with the rest of the crew drinking bottled beers, sharing stories and watching the cityscape transform. By dusk a low mist had begun to obscure most of the buildings. The iconic dome of St Paul’s temporarily disappeared before re-emerging, floodlit, against the London skyline. Red- flashing beacons began to appear sporadically through the fog, marking the tops of tall cranes and skyscrapers. The skeletal frame of the Shard came suddenly into focus as every floor of the tall skyscraper lit up simultaneously. At the same time the beautiful gothic structure of Tower Bridge behind us was illuminated from above and below, throwing a sparkling reflection into the black waters of the Lower Pool of London – a place where so many of the world’s most important ships must have anchored at different points in time. As night fell the lights inside all the flats, hotels and offices along the riverside came on. We floated in the dark void of the river, suspended in time.

On the water the sounds of the city seemed altered. I could hear the distant hum of traffic on the bridge, the clatter of trains rumbling past, the intermittent backdrop of sirens wailing, but it was as if these sounds were coming from another place altogether, not from the great throbbing metropolis around us. I sat and watched the vast twin bascules of Tower Bridge being slowly raised. A Thames Barge sailed silently past and drifted beneath the bridge before quickly disappearing into the shadows on the other side. On the remains of a wooden jetty nearby, I could just make out the shape of a large black cormorant standing perfectly still with its great wings outstretched.

Eventually we all went below deck into the former hold of the boat, which now served as the living quarters for the male members of the crew, with a small galley kitchen at one end and a large wooden table and chairs in the centre of the open plan space. Ben asked us to gather around the table to examine a nautical chart of the Thames Estuary. We spent the next hour or so deliberating over the definition of that place; all we could agree on was that the estuary encompasses the stretch of water between the River Thames and the North Sea. Defining its outer and inner limits seemed almost impossible, as the fluid boundary lines shifted constantly throughout our discussion.

We argued for some time about where the royal river ended and the estuary began. I told the group I had been looking at eighteenth- and nineteenth-century Admiralty charts in the British Library’s map room; beautiful hand-drawn documents, covered in a mystifying array of complex lines, which had been difficult for me to decipher but at the top of a chart dated 1871 the Thames Estuary was described as being: ‘18 nautical miles long from Gravesend to the Nore’. Some members of the crew thought it was much longer than this, starting as far upriver as Tower Bridge – the ancient control centre of the Estuary. Others felt the Thames Barrier or even the QE2 Bridge were obvious beginnings. But most agreed that before these structures were erected the historic gateway into the Thames for centuries had always been the ancient shipping port of Gravesend, which sits at Lower Hope, the narrowest point in the river, a place of strong tidal currents where the brackish dirty water from London merges with the salt water from the North Sea.

Leaving London the inner estuary is generally believed to end somewhere around the forbidden military zone of Foulness Island, which sits opposite the site of the former Nore light ship. However a Hydrological Survey, dated 1882, states that the eastern boundary of the outer reaches of the Thames Estuary stretches much further out into the North Sea, from North Foreland near Margate across to the Kentish Knock Lighthouse in Harwich. The sailors in the group agreed with this definition although the contemporary chart we were looking at showed the outer limits of the Estuary extending all the way up to Orfordness on the Suffolk coast.

The boundary line for the beginning of the inner estuary was thought to be somewhere near the head of Sea Reach, south of Canvey Island, although I felt it could originate as far along the Essex coast as the Crowstone, which sits just off the foreshore of Chalkwell Beach. The first of the ancient stone obelisks to be placed there in 1197 was referred to in official records as the city stone of Leigh. The base of this medieval stone may still rest under the mud but the original marker has long since disappeared. The monument that exists there today is made of granite and looks similar in shape to Cleopatra’s needle on the Embankment. It was erected there in 1836 but an older version sits amongst the rose beds in Priory Park in Southend.

You can walk out to the Crowstone easily when the tide goes out. Inscribed on the north, east and west faces are the names of the lord mayors of London who used to visit every seven years for the water pageants that once took place around this local landmark. In Southend Library I had read eighteenth-century descriptions of these ceremonies, which told of great processions from London by steamboat, with the Lord Mayor being accompanied by water bailiffs, sheriffs and the aldermen of the city. The ceremonies were performed to huge crowds of people and would begin with the city sword being placed against the stone, ‘an act which signified the official maintenance of the claim of the city of London of the jurisdiction of the Thames at this limit mark.’ At high tide city officials would row around the Crowstone three times before drinking the toast ‘God Preserve the City of London.’ At low tide entertainment was provided for the spectators with the local sheriff being ‘respectfully bumped’ against the stone by watermen, after which he obtained the Freedom of the Water. The proceedings would continue with a huge amount of drinking and merriment followed by ‘a scramble in the mud for coins, usually one hundred newly coined sixpences, thrown to the crowd by the mayor.’ The same ceremony would then be repeated on the other side of the river, at the London Stone, which sits directly opposite the Crowstone at the entrance to Yantlet Creek on the Isle of Grain. The imaginary line between the Crowstone and the London Stone is called the Yantlet Line and denotes the final end of the Thames. As a child I was told the Yantlet Line is the place where London ends and Essex begins.

The London Stone has become a mythical pilgrimage site for a number of artists and writers recently who have risked their lives to touch it at low tide. In fact I had been listening to the writer Iain Sinclair tell a story about such an adventure the night when I had first met Ben Eastop, the owner of IDEEAL. In the former drawing room of the old manor house of Chalkwell Hall, which overlooks the Thames Estuary in Essex, Iain spoke to a crowded room of people about his recent explorations around the marshland territory off the North Kent coast, where he reached the London Stone on a swan pedalo with the artist Andrew Kotting:

‘In Ghost Milk, a book I wrote as a charm against monolithic Olympic enclosures in the Lower Lea Valley, I decided that I needed to actually touch the London Stone, as a physical marker for the start of the tidal Thames. I was going to walk the river, from mouth to source, as a way of taking the temperature of the softest part of Middle England. But you can’t reach it! The Stone is on unmapped military land. I spent four days trying to get in and being turned back by razor wire and the wives of policemen. I finally managed it with the photographer Stephen Gill. We carried a kayak to the mouth of the Yantlet Creek. But we didn’t need it, the tide was out. We walked across. So the return on the swan pedalo from Hastings, with Andrew Kötting, was like a final gesture against those Olympic enclosures. We rode the tide, saluted the Stone, and read from my earlier book, Downriver.’

After Iain’s event Ben approached me and asked if I would be willing to be the writer-in-residence for a multi disciplinary arts project he was organising, responding to place. The idea was to take a five-day experiential cruise on IDEEAL along the Thames Estuary with a mixed crew of visual artists, an archaeologist of the recent past, a musician, a filmmaker, a writer and an ornithologist. ‘The journey will be deliberately slow paced,’ he said, ‘allowing those on board a direct and immersive experience of this ancient waterway during a crucial period of change.’ We aimed to amble downriver, to drift on the tides, to meditate on the unique seascape of that place.

The idea appealed to me immediately as the estuary and the mud flats of the Thames had been the landscapes of my childhood. I had grown up in Southend-on-Sea on the Essex coast and spent my school holidays paddling, swimming and playing in the Estuary waters. When the tide went out, I walked out on the mud for miles, catching crabs and shrimp in the little pools of water left behind by the receding sea. I knew the dangers of the incoming tide and also knew something of the military history of the place, having visited the remnants of crumbling forts along the coastline. I knew the stories of the ship filled with bombs sitting on the riverbed, but before my trip on IDEAAL I had never actually spent any time on the water itself. Most Estuary dwellers haven’t either. For the majority of people who live in the many towns and communities dotted along the Essex and Kent coastlines the Estuary is little more than a much loved scenic backdrop to their lives. It remains, for most, an unknown landscape.

It was late on that first night when I finally settled into my cabin in the stern of the boat, which I was sharing with the only other woman on the crew, the archaeologist Sefryn Penrose. I lay awake, feeling the weight of IDEEAL in the dark water, listening attentively to the creak of old wood and the sound of water lapping against the hull, whilst inhaling the strange odours inside – a mix of paraffin, old rope, wood and dust. In truth I was nervous about the journey ahead; before that night I had never spent more than an hour or two on a boat.

Eventually I must have fallen asleep, as the vibration of the diesel engine above woke me at six am. Crawling out of my bed I made my way into the former cargo hold next door. Abandoned sleeping bags and mattresses lay scattered around the floor; the rest of the crew were up already. I helped myself to the remains of the still warm coffee in the pot and sat for a while in the belly of the boat, thinking about the merchandise that once filled that space: potassium, tea, spices, bricks, hay, anything that needed moving from one place to another. Ben had told me that when the vessel was used as a privately owned taxi service for shifting goods around the Dutch canals the great curved solid steel beams on the ceiling could be removed to throw large loads into the hold.

Tentatively I climbed the almost vertical wooden ladder up onto the deck. The sun was shining brightly and London looked magnificent. Ben was standing in the wheelhouse next to the musician John Eacott, the only other experienced sailor on the crew. Everybody was in good spirits and we were ready to begin our first day cruising along the Estuary; the start of what would become for me a deep exploration of that place.