Live pipeline welding is required to complete operations and maintenance activities on natural gas networks. Industry standards and UK guidance advise that live hot works on hydrogen pipelines should not be undertaken at present. In the UK, network operators are investigating repurposing transmission pipelines from natural gas to hydrogen as part of the UK’s net zero commitments. The Local Transmission System (LTS) Futures programme is a first of a kind, £30 million, joint project between OFGEM, SGN and the other UK gas networks. As part of the programme SGN modified, tested and validated existing natural gas live welding procedures and processes for hydrogen pipelines in collaboration project partners ROSEN, PIE and T.D. Williamson. Welding procedure specifications (WPS) were developed and qualified through robust and extensive investigations using software simulations and at an offsite testing facility. A test loop was constructed using pipeline material taken from the LTS. This was pressurised with gaseous hydrogen and allowed for static and flowing tests. Preliminary offline tests were completed ensuring recommended inner pipe wall temperature limits were not encroached and to evaluate weld penetration. Pre-heat decay times and weld cooling rates under varying hydrogen flow rates and pressures were investigated. Provisional WPS’s were produced and used for welding two full size split tee fittings onto the pipe material in the test loop. Following welding and non-destructive testing, one fitting was sectioned and mechanically tested for procedure qualification, the other was used in a full-scale fatigue test. Project WPS’s were created and used by T.D. Williamson’s experienced and qualified in-service welders during a full process run-through and assembly mock up to confirm usability and finalise the WPS’s. The WPS’s were subsequently used to field weld a split tee onto the repurposed LTS Futures 457 mm diameter pipeline in Scotland containing flowing high pressure gaseous hydrogen.