Essex Police Marine coppers have always had a demanding job. They have the longest coastline of any British county as their patch. Their beat was described by their team boss, Insp Thurkle, as “one big crime scene.”

Now it’s part of history. This month, the Essex Police Marine section officially ceased to exist. Following its amalgamation with the Kent marine force, the combined units now operate under the new title North and South Marine Unit.

“We’re not even supposed to use the word Essex any more,” says one long-serving officer, Det Con Simon Lofting.

The Essex Marine Unit had just celebrated its 62nd birthday. That may be a lot of water under the bows, yet the Essex unit was, one of the youngest of its kind. Despite the county’s exposure to the sea, Essex Police were slow to launch bobbies in boats. Even some landlocked counties, such as Oxfordshire, managed to beat Essex.

London’s river police force, founded by Essex farmer John Harriott, began life as early as 1839. Essex had to wait until 1949.

The comparisons with today’s situation are telling. Then as now the big issue was cost. Essex chief constables held out against the expense of founding a marine unit for a long time, despite pressure. They managed to hold the line until 1949 by sticking to a simple principle. Let someone else cover the waterfront. Body in a creek? Pay a couple of wildfowlers to retrieve it in one of their 18ft punts. Shipwreck in the estuary? Port of London Authority’s job.

Unsurprisingly, other organisations saw things differently. In 1914, the Port of London Authority wrote a stiff letter of complaint to Essex County Council. Did they not appreciate that “the lower reaches of the Thames from Dagenham to the sea are totally unsupervised?”

“Is it not time for Essex to take steps to protect its own waterfront?” they demanded.

The council politely acknowledged, then in best maritime tradition turned a blind eye for another 36 years.

Eventually, in despair, the Met issued a confidential ultimatum to the chief constable of Essex, Sir Jonathan Peel. Do something about the lower Thames, or we will take matters into our own hands, cross the county line, and do the job ourselves.

It was an extraordinary situation. One police authority was threatening to invade the waters of another.

Bowing to pressure, Peel authorised the setting up of a marine force. He kept it as small as possible, referring to it disparagingly as “a presence on the river”.

It consisted of a sergeant and four constables, all volunteer PCs with some sort of maritime experience.

Police sergeant Sidney Cranfield was an ex- Merchant Navy man, the constables consisted of an ex-submariner, a former naval telegraphist, a coastal master mariner, and a yachtmaster.

The first craft was a rather battered tender, Vigilant, acquired from, of all people, the RAF.

Just ten months after it was founded, in January 1950, the Marine Unit endured a baptism of fire. Along with the Southend and Sheerness lifeboats, it responded immediately to the sinking of the Royal Navy submarine Truculent following a collision with the Swedish tanker Divina in the Southend estuary.

Most of Truculent’s crew managed to reach the surface via the escape hatch, but 57 of them died on the surface.

Many were swept away by the currents of the estuary. Others managed to reach mudflats.

The crew of the Vigilant searched desperately for these survivors, but many had frozen to death by the time they were discovered.

The tragedy at least served to prove the value of the Marine Unit. From this time onwards it began to expand. Following the Truculent disaster, escort launches were made compulsory for all incoming or outgoing naval vessels.

This became a regular feature of the Vigilant’s work, along with onboard searches of vessels, boat recovery, marine theft, immigration, transport of special operations personnel, marine accident investigation, boat recovery, counter terrorism, and, in recent years, wildlife protection.

The force almost tripled, both in personnel and resources, between 1960 and 1980. This was largely to meet the huge growth in pleasure boating along the Essex coast, and the even bigger growth in marine crime.

It is hard to understand why Essex Police bosses ever thought they could do without a presence on the water.

In 1978 Vigilant was replaced by a purpose-built vessel which became the icon of the Essex Marine Unit, Vigilant II. Fast and graceful, she became a familiar feature of the estuary and Essex coast.

She can be seen in the background of numerous photographs covering events such as the Thames Barge Race.

Vigilant was finally retired in 1979. Changing technology means that much of the work once done by her and other launches is now performed by fast rigid inflatables and by single officers on jet skis.

The boats may have changed, but the workload goes on increasing. There was £50,000 worth of theft related to boats in January 2011 – and that is considered a quiet month.

In another area, the Marine Unit has become responsible for counter-terrorism operations in the Thames Estuary, including prevention of an underwater attack on London.

The Essex Police marine section may no longer be an independent unit, but in some ways the amalgamation with Kent marine police marks a return to its origins.

In July 1949, one of their first routine patrols, the crew of Vigilant made a liaison with another launch. It belonged to Kent police.

The two crews struck up an informal deal. Whoever was on duty would keep an eye on the other county’s shoreline.

Now 62 years later, the Essex-Kent amalgamation means that deal has finally been made formal. Once again, history has repeated itself.