Lizard or Newt..?

I nearly (accidentally) cut this little cutie in half with a pair of garden shears...
I found another five of them in the undergrowth...
Having tried, and failed, to identify it I have abandoned my ambition to become a top naturalist al-la David Attenborough...
For any top naturalists reading this, who wish to further expose my ignorance, it had an orange underside...