The private meeting at a London hotel aimed to revive the deadlocked six-party talks. Pyongyang withdrew from the aid-for-disarmament talks in 2009, and over the past year it has made clear it wants to be treated as a nuclear weapons state.
Stephen Bosworth, a former US special envoy for North Korean policy, said the meeting was "cordial and respectful." He declined to comment on what was covered or whether it made any progress.
"That's a question for governments, not for me," said Bosworth.
China and Russia have supported efforts to get the dialogue with North Korea back on track, while South Korea and Japan both remain suspicious of calls to restart the talks.
Britain's Foreign Office confirmed that North Korean officials were in the UK for informal diplomatic talks. It said British officials, who are not part of the six-party framework, will meet with Pyongyang's Vice Minister Ri Yong-ho separately as part of bilateral relations.