When William V's father William IV, Prince of Orange died in 1751, the young prince was only three years of age. His mother Anne, Princess Royal and Princess of Orange became Regent for her son in as far as the hereditary office of stadtholder was concerned. Before his death, however, William IV had already made arrangements to give the Duke a role as her adviser. In any case, the ancillary office of Captain-General of the Dutch States Army could not be exercised by a woman, and the Duke was appointed its Captain-General. The Duke remained in this position during the subsequent regencies of Landgravine Marie Louise of Hesse-Kassel and Princess Carolina of Orange-Nassau. During this entire period he had great influence on the prince's education, and an almost father-son relationship developed between the two.
In the eyes of contemporaries the young prince had not fully matured before he reached his majority on 8 March 1766, and became stadtholder in his own right. The class of ruling Regenten therefore felt anxious about his taking the reins of power unchecked, and the pensionary of Delft, Pieter van Bleiswijk, a leading member of the States of Holland and the States General of the Netherlands for Holland, together with other grandees, like the Grand Pensionary Pieter Steyn took the initiative of making an arrangement in which "for the time being" the influence of the Duke would be informally continued. This was formalized in a contract (which later became known as the Acte van Consulentschap or Act of Advisorship), drawn up by van Bleiswijk, and concluded between the Prince and the Duke on 3 May 1766. Both signed it, and the Duke swore to it, according to the witness, the Princes' secretary, F.J. de Larrey
The Act consisted of our articles.
The Act remained secret for a long time, but of course the inner circle around the Prince knew about it. If necessary, the Duke would brandish it, if challenged by other courtiers, like Willem Bentinck van Rhoon. The immediate effect of the Act was that an attempt to saddle the stadtholder with an "advisory council" was thwarted.. As will be clear from the above account of the contents of the Act, it did not give the Duke formal powers over the stadtholder, but it helped him exploit the natural ascendancy he had enjoyed over William from an early age. The relationship helped to perpetuate the dependence of the younger on the older person to an "unhealthy" extent, as was recognized by many in their environment. The Duke was instrumental in obtaining the hand in marriage of Wilhelmina of Prussia, Princess of Orange, a niece of the Prussian king Frederick the Great, whom William married on 4 October 1767, but the Princess soon started to resent the Duke's influence, and she became one of his main opponents.