The admirals of the Soviet Union declared North Korea’s prize submarine to be obsolete back in 1961, and Western experts stubbornly point out its inability to sink enemy vessels.

But Kim Jong-un, the “Supreme Leader” of North Korea, offered navigation tips and issued stern battle orders during a proud tour of a Romeo class submarine of the People’s Navy.

Designed in the 1950s, the vessel was in production for the Soviet Union for only 48 months until being succeeded by nuclear-powered submarines 53 years ago.

Every other navy in the world then gave up on the Romeo, with its noisy and easily detectable diesel engine – apart, that is, from North Korea’s.Today, the country has 20 Romeo class boats, comprising almost a third of its submarine fleet.

During his visit, pictures of which were released on Monday, Mr Kim mounted the vessel’s conning tower and went on a short voyage, during which the official news agency reported that the multi-talented leader “taught” the submarine’s captain a “good method of navigation”.

Mr Kim also urged his commanders to think “only” of “battles” and “spur combat preparations”.

Any captain of a Romeo class submarine might, however, view hostilities with trepidation.

The boats carry Yu-4 torpedoes, a Chinese-made weapon dating from the 1960s with a range of four miles.

The Los Angeles Class nuclear-powered attack submarines of the US Navy, meanwhile, carry Harpoon missiles that can sink a ship 150 miles away.

The North Korean vessel is a “basic” model with “virtually no anti-submarine performance”, says IHS Jane’s Fighting Ships.

This means the Romeo might try damaging a ship – provided it happens to be less than four miles away – but it would be helpless against an enemy submarine trying to send it to the bottom.

At least one North Korean submarine has gone to the bottom without any help from the country’s enemies.

A Romeo class boat sank in an apparent accident in 1985.

Of North Korea’s 20 submarines in this category, seven were supplied by China between 1973 and 1975 and the rest built in the country’s own shipyards between 1976 and 1995.

More than three decades after the Soviet Union had stopped making the vessel – and after it had been phased out by the navies of Syria, Algeria and China – North Korea was still producing its own version of the Romeo.

Mr Kim’s decision to pay a high profile visit seems at odds with the official doctrine of the so-called People’s Navy, which stresses the importance of camouflage and concealment.

So seriously were these tasks taken that 2004 was officially declared the “Year of Camouflage”.

On the 10th anniversary of that occasion, however, Mr Kim allowed photographs of the unlikely pride of his fleet to be released to the world.

Cdre Stephen Saunders, the editor of IHS Jane’s Fighting Ships, summed up: “The fact that the Dear Successor is spending time on what, in any other navy, would be an obsolete submarine tells its own story.”