I'm in the process of renovating a 1950's ish council house. We found a 4.16 mbar drop during a gas tightness check so investigated the pipework. The leak was found on a 15 mm copper joint and repaired. Our investigation showed that an original lead pipe had been repaired with copper (see pic). Would it be within the Gas Safe regulations (done by a 'competent person') to join the lead pipework like this today?