The ship HMS Tyne left England taking Swainson and two other prominent figures in the future of New Zealand law, the Hon Sir William Martin, who was to become the first Chief Justice, and Thomas Outhwaite, who was to become Registrar of the Supreme Court in Auckland, to New Zealand.

On the ship the three men began to draft "in simple, concise and intelligible language" a new system of laws which they planned to be ideal for the new colony of New Zealand.

[2][3] Within six months of their arrival in New Zealand on 25 September 1841, 19 enactments had been passed creating the basis of governance in the new colony.

[2] Swainson frequently defended the interests of Māori on the issue of land claims from settlers, notably over disputes concerning the Treaty of Waitangi, which had been signed in 1840.

Swainson was appointed to the subsequent New Zealand Legislative Council (the upper house) on 26 May 1853 and became its first Speaker, from 16 May 1854.

Willoughby Shortland, the Colonial Secretary for New Zealand, who was also at the meeting, asked Swainson to prepare a paper about this.

Stanley's Undersecretary, James Stephen, said that although the declaration of sovereignty might be an unjust breach of faith, it should stand.