Even as an ex-early years teacher it's new to me. When I taught in schools the children learnt their letters using the 'Letterland" system. These were letters that all had a colourful character attached to it and a song/ story for each character to help them pronounce their letter sounds correctly.
"Jolly Phonics" is very similar but instead of covering just the first 26 letters it incorporates all 42 phonemes.