He was now in the direct way to preferment.
Early in the following year (March, 1601) he succeeded to the place of assistant to the principal master shipwright at Chatham, and undertook the repairs of Her Majesty's ship The Lion's Whelp, and in the next year he new-built the Moon enlarging her both in length and breadth.
At the accession of James I.in 1603, Pett was commanded by the Lord High Admiral with all possible speed to build a little vessel for the young Prince Henry, eldest son of His Majesty.

It was to be a sort of copy of the Ark Royal, which was the flagship of the Lord High Admiral when he defeated the Spanish Armada.

Pett proceeded to accomplish the order with all dispatch.

The little ship was in length by the keel 28 feet, in breadth 12 feet, and very curiously garnished within and without with painting and carving.

After working by torch and candle light, night and day, the ship was launched, and set sail for the Thames, with the noise of drums, trumpets, and cannon, at the beginning of March, 1604.