Nevertheless the invasion of England is not an easy task and requires command of the sea, which Warwick possessed. He has often been criticised for his military shortcomings but he was a very able admiral and popular with his sailors, many of whom had defected from Henry VI's forces to join him.
The Yorkists published a manifesto from Calais which was a pretty standard late medieval proposal of rebellion, promising loyalty to the King but attacking his advisers especially, in this case, Shrewsbury, Wiltshire and Beaumont. (The Queen and Prince were not mentioned; more surprisingly nor were Exeter and Pembroke.)
Lord Fauconberg (Warwick's uncle) led an advance party to secure a bridgehead at Sandwich, and on 26 June Warwick, Salisbury and March landed there, accompanied by the Papal Legate, Francesco Coppini, who was accredited to Henry VI. They were received by no less a person than the Archbishop of Canterbury, Thomas Bourchier, later to crown Edward IV, Richard III and Henry VII in his long career. They recruited heavily in Kent, a strong area of Yorkist (and more particularly Neville) support. London fell to them on 2 July without resistance, although the Tower held out under Lord Scales.
The Yorkists had already given Coppini a written pledge of their loyalty to Henry VI, and given the Kentishmen/Men of Kent the same line. Warwick now swore a public oath of loyalty at St. Paul's, although he used the occasion to set out their principal grievances once more. It is likely that the Londoners were sympathetic, but they would also have been keen that the Kentish Brigade should not get out of hand (as they had at the time of Cade's Rebellion, 1450) and the leadership at least probably feared to burn all their bridges with Henry VI. The oath was politically convenient all round.
Salisbury remained in London to conduct a siege of the Tower, but Warwick, March and the bulk of the army marched north. A very considerable royal army was in the field to meet them and on 10 July the forces met at Northampton.