Kim Jong-un has offered to cease all nuclear testing in advance of a meeting with President Trump

North Korea’s nuclear test site is believed to have collapsed, rendering the secret base unusable and potentially explaining Kim Jong-un’s newfound willingness to discuss ending his weapons programme.

At least five of North Korea’s six nuclear tests have been carried out at Punggye-ri, in the northeast of the country, at a site carved out of the 7,200ft Mount Mantap.

Scientists who have studied seismic data from the region now believe that part of the mountain collapsed during the most recent test in September.

The test on September 3 had a yield of 250 kiltons — almost 17 times as strong as the Hiroshima bomb — and caused a 6.3-magnitude earthquake.

Approximately eight and a half minutes later another seismic event was recorded. The 4.1-magnitude tremor