Born in 1840 in Barnagar, five miles north of Kolkata, Sasipada Banerji was a reformist Hindu who married a thirteen-year-old girl, Rajkumari Devi, in 1860. However, he refused any dowry and began to teach her to read and write a year after their marriage. Banerji joined the Brahmo Samaj in 1861 and was involved in the social reform movement in West Bengal.

Sasipada Banerji met Mary Carpenter on her visit to India in 1866 and she subsequently invited him and his wife to visit her in England to educate British people on the cause of female education in India. Despite some hesitations about crossing the kalapani (black waters) with his wife, Banerji took up the offer and left India on 19 April 1871. He believed that his wife was the first Brahmin lady to cross the seas to visit Britain.

In Britain, Banerji was welcomed by the Secretary of State. He joined the Good Templars Body and became a member of the Order of the Day Star Lodge. He lectured on temperance, female education and working men's movements. He attended National Indian Association meetings and established branches of the NIA in other cities in Britain. His son was born at Mary Carpenter's house, Red Lodge, in Bristol on 10 October 1871, and was named Albion; Mary Carpenter wrote to Colonel Posonby, the Queen's Private Secretary, to inform her of the birth of what they believed to be the first British born Indian. Banerji returned with his family to India in 1872, his wife Rajkumari died in 1876 and he re-married in 1877.