Geri Halliwell says she was holding back the tears when she watched the workshops of the new musical.
Mel C added that the rehearsals gave the girls "goosebumps" and it was a "lovely thing"
The girls said the musical supports Girl Power's longevity. "Who would have thought the message is still standing 16 years later".
More top news
Councils will have to cut money from services such as libraries because of the rising cost of caring for the elderly, a new report warns.
A Branislav Ivanovic header in extra-time ensured that Chelsea are through to the Capital One Cup Final after beating Liverpool
Scientists have discovered the oldest known earth-size planets discovered which they say raises the prospect of 'ancient life'.