In 1639, Leyel was appointed as head of the Christianshavn and was to inspect the financial conditions caused by Governor Bernt Pessart in India.

However, in early 1640 during her voyage, Christianshavn was detained and Leyel subsequently spent the next three years negotiating with Spanish officials for her release.

[2]The first time we have reliable information about Willem Leyel, he was employed by the Dutch East India Company in Batavia.

[3] Louis de Dieu in his Historia Christi mentions Leyel briefly:[3] I owe it to the Danish merchant Willem Leyel to confess that the information that this man, raised above the ordinary spirit of commerce, though no scholar, while he still lived in Persia, learned to speak, read, and write the Persian language, passed on to me, when he spent some time in Leyden, has been very usefulIf it is true that Leyel spent time in Persia, he may have arrived in 1623 when the first Dutch commercial expedition arrived in Persia and succeeded in establishing a trading post.

[4] However, Leyel could not have been there for long, since in 1626, we find him, together with his comrade, Claus Rytter, at Pipili, where the Danes had made attempts to make a foothold.

[10] However, at Santa Cruz, the ship and captain were inspected by the Spanish, who were skeptical of other European nations trading and colonizing India.

[15] Arriving at Madrid, Leyel issued a complaint about the treatment he and his men had received and demanded that Christianshavn be released on behalf of the Danish king.

[17] After much effort, Leyel's complaint reached Spanish officials, and after heavy negotiation, Christianshavn could finally be released.

[25] As a response, Leyel immediately sent out Jørgen Hansen with a longboat and a strongly armed crew to catch Pessart.

[29] However, in the letter, the officers at Dansborg rejected the removal of Pessart as governor, and Leyel was thus compelled to take control of the fortress by force.

[30][28] With 70 black and white men, Leyel went ashore and besieged the fortress with the help of the local population and the Thanjavurian Nayak.

Indian bricklayers and carpenters were set to rebuild the walls and repair the woodwork of Dansborg, and after time many of the houses were torn down and rebuilt.

[41] The news of this slowly reached India, and it gradually became evident to Leyel that neither the King nor the Company had any means to send new ships to the East.

[45] Leyel promised the Portuguese refugees security of life, and some of them were employed by the Company as soldiers and minor officials, while others took part in the regional trade.

[41] Because of Pessart's unorthodox commercial strategy[48] and exponential debts, trade with Ceylon, Masulipatnam and Makassar was in total disorder.

[33] Leyel nonetheless still found Makassar to be the best place for trade on the Sunda Islands, and he hoped to pay off Pessart's debts there.

Wirta from Leiden University, the Danish Company had three regular trade networks: The first was with Ceylon and consisted of arrack, cinnamon and elephants, all of which were key products.

[52] At Bantam, Herman Clausen had built up and organized the Danish trading station, however, he became seriously ill and was transported by the Dutch to Tranquebar where he would soon after die.

In 1644, the acting governor of Tranquebar, Anders Nielsen, was sent to Ceylon with gifts to the local ruler,[58] and the king of Makassar still viewed the Danes favourably.

[63] Evidently, the Dutch had supported the Thanjavurians in their siege on Dansborg in 1644 and had tried bribing the local Nayak to give them Tranquebar the same year, however, without success.

[64] In 1645, the privateering war had harmed the Bengal interests so much that they sent a Jesuit, Antonio Rodríguez, to Leyel to reach a settlement.

[65] Leyel was requested to estimate the combined Danish losses through Bengali injustices, however, they could not reach an agreement, and fighting intensified instead.

[67] At once, Leyel also felt obliged to declare war on the Sultanate of Golconda, and after the seizure of a couple of ships, the two parties agreed to a peace settlement.

[28] The peace settlement with Golconda effectively put an end lucrative privateering market, which the Danish seamen and officers had been heavily involved in.

[72] Leyel had probably hoped for a coat of arms and greater recognition such as his predecessor, Roland Crappé, had obtained, yet he had to be grateful for the supply of rations so that he could sustain his life.

Apart from Danish, Leyel seems to be able to speak Latin, German, Dutch, Spanish, Portuguese, Persian and possibly also Arabic and English.