That's the other guy I heard on R4 - the former head of immunisation at the dept of health, calling for focusing on the first dose.
Use everything you've got as fast as possible, offer more people some protection, especially given this more contagious new strain.
Parliament seems to be against it because it would need new approvals, as someone pointed out. Doesn't seem a good enough reason to me, should processes hold us back at this stage? They've thrown everything up in the air at a moment's notice for businesses and families this year.