Which of the following cases upheld ‘secularism’ as a basic feature of the Indian Constitution even before the word ‘secular’ was inserted in the Preamble?

In Kesavananda Bharti case ,The Constitutional Bench, , ruled by a 7-6 verdict that Parliament should be restrained from altering the ‘basic structure’ of the Constitution.The court held that under Article 368, which provides Parliament amending powers, something must remain of the original Constitution that the new amendment would change.The court did not define the ‘basic structure’, and only listed a few principles — federalism, secularism, democracy — as being its part. Since then, the court has been adding new features to this concept.