AIM: Sub30 study is an open-label, prospective, single-arm feasibility study with the primary objective of assessing the logistics, feasibility, and safety of ECPR delivery in a pre-hospital setting for refractory out-of-hospital cardiac arrest patients in London, United Kingdom. RESULTS: Forty-three eligible patients were identified by London Ambulance Service over 27 trial recruitment days during a 13-month study period resulting in the despatch of the pre-hospital ECPR team to 18 patients. Five patients met full criteria and were cannulated for ECPR. All patients were male with a median age of 61 years and received ECPR full flows at a mean of 47 min (range 37-59 min) from initial collapse after a median travel time to scene of 14 min (range 3-20 min). No patient met the primary outcome measure of being established on pre-hospital ECPR within 30 min of the call to the emergency services. Out of 5 patients, 3 patients had treatment withdrawn and 2 survived to hospital discharge (both CPC score 3 and modified Rankin Score (mRS) score 4 and 5 respectively). METHODS: Open-label, single-arm, feasibility, prospective study. CONCLUSIONS: Whilst our study did not meet primary outcome of achieving full ECPR flow within 30-minute of collapse, it demonstrated safe, timely and effective delivery of ECPR with comparable survival rates by pre-hospital teams in a large metropolitan city and this has potential to improve outcomes in refractory out-of-hospital cardiac arrest patients.