Hopper (2007:1-4) ("'Black Tom': Sir Thomas Fairfax and the English Revolution") provides a vivid account of the meeting and its important role in the period leading up to the civil war.
He sent a message to both houses of Parliament, and afterwards advanced to Hull, to secure the arsenal there which had been left in that town, upon the disbanding of the army raised to oppose the Scots in the Bishops War; but, on being denied admission by Sir John Hotham, the parliamentary governor, he returned to York.
On their passing an ordinance for embodying the militia, the king ordered his friends to meet him in York, whither he directed the several courts to be in future adjourned.
[1] On 27 May 1642, the king issued a proclamation from his court at York, appointing a public meeting of the nobility and gentry of the neighbourhood to be held at Heworth Moor, on 3 June.
Charles returned from the meeting to York, where, after keeping his court for more than five months, during which time every attempt at negotiation had failed, he advanced to Nottingham, and there erected his standard on 22 August 1642.