Ahead of a summit with President Vladimir Putin, North Korea’s leader Kim Jong Un has announced a surprise visit to Russia. The Kremlin said the meeting would be about weapons supplies for Moscow's conflict in Ukraine. Gracing the tracks with his presence was Kim Jong-un, who recently travelled to Russia by train. According to reports, while President Putin flew off on board a luxuriously furnished and heavily armoured private train that moves at a leisurely pace due to its weight, it is believed that Kim Jong-un’s train can only reach speeds of 59 km/hour, far slower than high-speed trains found in London and Japan.

It is reported that Kim Jong-un’s father and grandfather had an aversion to flying, possibly because they witnessed a jet explosion during a test flight. No North Korean leader since then has flown abroad by air for more than three decades, until Kim last week, when he headed off for Russia.

Kim Jong Un is a sporadic flyer, including while in Swiss boarding school, but he prefers the train, perhaps as an homage to family tradition and his elders. The green armoured train has 21 bulletproof carriages with plush interiors that make it safe and luxurious.

It offers logistical advantages: one train handles security checks on the railway tracks; another carries bodyguards and support personnel. When travelling by train, every square inch can be searched thoroughly; when the power is turned off at stations, other trains cannot move.

Kim’s visit to Russia will be substantial. Discussions will mainly centre on advancing relations between two neighbouring nations whose previous arms deals have been denied, though both countries have pledged closer defence ties.