London - Beijing - Pyongyang - Beijing - London

Can you advise whether the above qualifies for the 72 hour visa-free transit on both legs of the trip? We would be flying from London to Beijing, have a stopover of about 50 hours before flying to Pyongyang. We would be staying in North Korea for 4 nights before flying back to Beijing. We would then have about 25 hours in Beijing before flying back to London.

Thanks