"Taking coals to Newcastle" - a phrase coined to describe a pointless exercise.
For centuries, the idiom was well-observed - especially on the docks of the River Tyne, from where vast quantities of the locally-mined fossil fuel were shipped abroad.
During their 1920s heyday, the docklands - now collectively known as the Port of Tyne - once handled 23 million tonnes in a single year.
Of course, the coalfields of north-east England have since been depleted, taking with them the river's most lucrative trade.
So how has the region's maritime economy survived, and is it still foolish to take coals to Newcastle?
In September 2007, the QE2 paid its first-ever visit to Tyneside, docking at the Port of Tyne.
The historic event was made possible by a £4m refurbishment of the 80-year-old Tyne Commission Quay - now renamed Northumbrian Quay - which was strengthened to accommodate the 295m cruise liner.
According to Andrew Moffat, finance and commercial director, it was the latest in a long line of improvements that have allowed the port to branch out.
New facilities made it possible for the QE2 to visit Tyneside for the first time
"There is a danger with relying on just one business like coal or cars, so we have always had a policy of diversification," he says.
"In terms of import and export, we've essentially turned into a 'one-stop shop'. We can bring in a container - via rail, road or sea - store the cargo in a warehouse and even carry out work on the goods.
"In other ports, you could end up with three or four different companies doing that.
"Then we have the passenger ferry terminal, plus we've had visits from 29 cruise liners this year - up from none in 2003."
Because the Port of Tyne is run as a trust, there are no owners or shareholders, meaning profits are re-invested in the facility.
Between 1983 and 1994, about £45m was spent on major infrastructure developments, including the car terminal, grain terminal, container terminal, transit sheds and the ferry terminal.
And since then, a further £100m has been invested as the port continues to adapt to changes in the world economy, says Matthew Hunt, commercial manager.
The port now has booming car export and ferry passenger businesses
"There's a trend at the moment for transporting goods in bigger and deeper ships, and we've had to react to this.
"For example, Riverside Quay at South Shields is our main cargo handling berth, and has been deepened and lengthened to accommodate Panamax-class ships.
"These are vessels of the maximum dimensions that will fit through the Panama Canal."
In April, the facility was named Port Operator of the Year in the Lloyd's List London Awards, beating off competition from much larger ports in Singapore, Holland and Egypt.
But it hasn't all been plain sailing. Rising oil prices recently led to the scrapping of the DFDS passenger service from Newcastle to Norway.
Mr Moffat admits the cancellation is bad news for the region.
"It's been a difficult situation for DFDS for some time, and it's not good for Tyneside because the customers won't come and spend money," he says.
"But in terms of the port, the impact is not huge. It's more of a historic loss - a passenger service between here and Norway has been in place for 50, 60 years and beyond.
"Obviously, it would have been better if the link had been maintained, and we'll continue to work with DFDS and other ferry companies in the hope that some kind of Norway service can be reinstated."
The interests of the Port of Tyne extend to the Far East, Australia, South East Asia, India, the Middle East, Canada and America.
The port is expected to import up to three million tonnes of coal in 2009
It exports about 500,000 cars per year, mainly from Sunderland's Nissan plant - widely considered to be Europe's most productive.
But of all the port's recent ventures, one has raised the most eyebrows.
In February, the Jin He, a Panamax-class vessel docked at the Riverside Quay.
It was carrying the largest cargo to have ever entered the Tyne - 61,727 tonnes of coal from Murmansk in Russia.
The return of coal to the river - albeit coming in the other direction - has been a resounding success.
Last year, the port imported almost two million tonnes of mostly Russian-mined coal, destined for Yorkshire, Liverpool and Scotland, to be used in power stations such as Drax.
During 2009, that figure is predicted to rise to three million tonnes per annum.
Proof, it would seem, that sending coal to Newcastle is no longer a fool's errand.