P.I.O. Application question?

Hello Everyone, I wonder if someone has any ideas on this question. I'm from England but my Grandfather was born in Lucknow, India in 1895. The family returned to England a few years later and I know that India doesnt allow Dual Passports. It's how I read the Indian Government Website I think I may be eligible to apply for an Indian P.I.O. Card. Does anyone know anything about this or have any ideas? Thanks Jason