In his first interview in the role, ambassador Choe Il said his country would continue its ballistic missile and nuclear programmes in spite of intentional warnings against them, and dismissed UN sanctions as having no legal grounds, and no effect.
“In regards to the sixth nuclear test, I do not know the scheduled time for it, as I am here in the UK, not in my home country,” Mr Choe said.
“However, I can say that the nuclear test will be conducted at the place and time as decided by our supreme leader, Kim Jong Un.”
Sky News asked the ambassador whether he was concerned about the prospect of US military action, which President Donald Trump’s administration has said is one of the options now being considered.
“If we were afraid of it, we probably would not have started conducting nuclear tests or launching ballistic missiles,” the ambassador said.
He added: “We are developing our nuclear strength to respond to that kind of attack by the US.
“If the US attacks us, our military and people are fully ready to respond to any kind of attack.”
He said a pre-emptive strike on his country would not be possible because they would turn US assets in the region “to ashes” at the first sign of movement towards an attack.
“The US cannot attack us first,” the ambassador said, adding: “If the US moves an inch, then we are ready to turn to ashes any available strategic assets of the US.”
Mr Trump has sent what he calls a “powerful armada” led by the USS Carl Vinson to the waters off the Korean Peninsula, where it has been carrying out exercises with South Korea’s navy.
However, the White House approach is at odds with the ambition of the new liberal South Korean President Moon Jae-in, who has spoken of his desire to bring “integration, unity and harmony” to the country.
Believing that confrontation has done nothing to stop North Korea from expanding its nuclear arsenal, his desire for warmer ties with Pyongyang has caused some concern.
A former top diplomat for East Asia described the election of Mr Moon as presenting a “risk of tension and divergence of opinion” between the US and South Korea.
The United States is currently thought to be readying new sanctions in the event of another nuclear test.
But in his interview, the ambassador said his country had been living under sanctions for the last six decades, and more sanctions would make no difference to their nuclear ambitions.
He denied his government’s pursuit of nuclear weapons was making the lives of his people harder.
“I do not think our nuclear development has made our people’s lives difficult. Our nuclear power is a result of the US’ hostile policy against us,” the ambassador said.
“Our nuclear power is our sovereign right. It is the only way to protect the peace of the Korean Peninsula and the region.”
He claimed UN Security Council sanctions were evidence of a double standard and had no basis in international law.
“The UN Security Council has been sanctioning against us whenever we launch missiles or satellites and carry out nuclear tests,” he said.
“As the sanctions do not have any legal grounds, we do not care about them, nor accept them.”
Sky News asked the ambassador whether his country would be prepared to stop anywhere short of a deliverable nuclear warhead – whether a formal peace treaty or the protection of China’s nuclear deterrent would convince them to suspend their programme and return to negotiations.
“The only way to protect our country is that we strengthen our power enough to suppress any enemy countries,” Mr Choe said.
“This is the only way to protect our peace and security. This is a lesson we felt in our bones.”
He said his country had learned the lesson of US military interventions elsewhere.
“As you have read in newspapers, the US has been attacking only the weak countries, including Afghanistan and Libya,” he said.
“They cannot actually attack the strong countries, although they talk about it.
“We have to have nuclear power. We have shown our strong military power and nuclear power this April. Because of our strong military power, the US could not attack us first.”
This was a rare and frank interview, and the bottom line is clear – North Korea intends to continue pursuing nuclear weapons, regardless of the consequences.