There is an interesting article called "My tryst with the legendary N. A. Palkhivala" written by Mr. H. S. Serna, IRS, published here.

Apart from that article, the following information from Wikipedia is also relevant.

Nani Palkhivala was called to the bar in 1944 and served in the chambers of the legendary Sir Jamshedji Behramji Kanga in Bombay. He quickly gained a reputation as an eloquent and articulate barrister, and was often the center of attention in court, where students of law and younger members of the bar association would flock to watch him. His excellent court craft and an extraordinary ability to recall barely-known facts rendered him an irresistible force.

N Palkhivala initial forté was commercial and tax law. Together with Sir Jamshedji, he authored what was then and still is today an authoritative work: The Law and Practice of Income Tax. Palkhivala was 30 years old at the time of the first printing. Sir Jamshedji later admitted that the credit for this work belonged exclusively to Nani.

Palkhivala first participation in a case of constitutional significance occurred in 1951, where he served as junior counsel in the case Nusserwanji Balsara vs. State of Bombay [(1951) Bom 210], assisting the esteemed Sir Noshirwan Engineer in challenging several provisions of the Bombay Prohibition Act. Before the year was out, Palkhivala was arguing cases himself, but his first case of constitutional import (a challenge of the validity of land requisition acts) was lost before the Bombay High Court.

By 1954 however, barely 10 years after his admission to the bar, Palkhivala was arguing before the Supreme Court. It was in this, his first, case before that court (concerning the interpretation of Article 29(2) and Article 30 of the Indian Constitution, which regulate the rights of religious minorities) that he first articulated his (later) famous statements on the inviolate nature of the constitution.