Sen by then had acquired an important position in the profession of design communication and became among the most sought after designers in France and across the world. He also got his French nationality in 1984. He continued to exhibit his paintings in different countries.
When India was partitioned 1947 to create Pakistan, a new country for Muslims, about 20 million people of Bengal and Punjab were displaced and brutally victimized. Sen’s wealthy, literate family had huge landed property in erstwhile East Bengal, the present Bangladesh, which was carved out to be East Pakistan for Muslims. So for being Hindus Sen’s family was overnight evicted from their home. Without taking any possessions, they fled for their lives amidst people warring over religion, and so became squatted refugees in West Bengal.