After he received his law degree he practiced law as an attorney at the Hof van Holland in The Hague for a number of years. His reputation encouraged the vroedschap of Amsterdam to appoint him as the city's second pensionary on 12 August 1762. He was promoted to first pensionary after the death of his predecessor in January 1774. He was the right hand of Egbert de Vry Temminck, the long-serving Amsterdam burgemeester, and together they were very influential in the States of Holland and West Friesland, where he represented Amsterdam. He was a rival of Grand Pensionary Pieter van Bleiswijk (he had been nominated as an alternate when the latter's appointment came up in 1772) and he therefore had a difficult relationship with that functionary, and also with the stadtholder William V, Prince of Orange, because as one of the leaders of the Dutch States Party regenten, he opposed the stadtholder's policies.[1]
Van Berckel was one of the driving forces behind the attempts to conclude a secret treaty of commerce with the rebelling American Colonies in the Neufville-Lee negotiations in 1778 which resulted in an unofficial agreement.[2] After a draft-treaty was found on the person of Henry Laurens, the intended American minister tot the Dutch Republic, when he was intercepted by the Royal Navy on his way to the Netherlands in 1780, Van Berckel was one of the people whose punishment was demanded by the British ambassador to the Republic, Sir Joseph Yorke. Criminal proceedings were instituted before the Hof van Holland, but when the Fourth Anglo-Dutch War broke out in December 1780, eliminating Yorke as a plaintiff, the case was dismissed. Nevertheless, Van Berckel was for a time not welcome as a member of the Amsterdam delegation in the States of Holland and States General.[1]
His position in the Amsterdam vroedschap was weakened when in February 1781 Joachim Rendorp, an Orangist and a personal enemy, became one of the Amsterdam burgemeesters.[Note 1] Van Berckel was formally removed from the Amsterdam delegation on 31 July 1781, which caused much resentment in Patriot circles, so that the Amsterdam city government relented, and reappointed Van Berckel on 20 November 1782.[1][Note 2]
Together with the pensionaries of Dordrecht (Cornelis de Gijselaar) and Haarlem (Adriaan van Zeebergh) Van Berckel became the leader of the Patriot opposition to the stadtholder in the States of Holland. He was active in the exploitation of the scandal, known as the Brest Affair. After the occupation of the Patriot towns of Hattem and Elburg by the Dutch States Army in September 1786 he was appointed in the special commission of the States of Holland that in reprisal deprived the stadtholder of his position as Captain-General of the Holland regiments in that army.[1]
After the Prussian invasion of Holland Van Berckel was mentioned as one of the culprits in the affair of the arrest of Princess Wilhelmina at Goejanverwellesluis by the Princess herself. He was therefore purged from all his government offices in October 1787. He remained a private citizen until his death in 1796[1]
