Right to Free Legal Aid was recognised as a Fundamental Right under Act 21 of Indian Constitution in the case of-

The recognition of the Right to Free Legal Aid as a Fundamental Right under the Indian Constitution occurred in the landmark case of Hussainara Khatoon v. State of Bihar, AIR 1979 SC 1360. This case played a significant role in upholding the right to legal aid as an essential element of ensuring justice, particularly for underprivileged and marginalized individuals who cannot afford legal representation.

Option B, M. H. Hoskot v. State of Maharashtra, AIR 1978 SC 1548, and Option D, Rudal Shah v. State of Bihar, (1983) 45 SC 14, are important cases related to the rights of prisoners, but they do not specifically address the Right to Free Legal Aid as a Fundamental Right.

Option C, Madhu Mehta v. Union of India, (1989) 4 SC 1548, is not a relevant case in the context of recognizing the Right to Free Legal Aid as a Fundamental Right under the Indian Constitution.

Therefore, the correct answer is Hussainara Khatoon v. State of Bihar, AIR 1979 SC 1360.