York and Warwick planned a fresh attempt from their secure retreats in Ireland and Calais; and in the midsummer of 1460 the Earls of Salisbury and Warwick, with Richard's son Edward, the young Earl of March, again landed in Kent.
Backed by a general rising of the county they entered London amidst the acclamations of its citizens.

The royal army was defeated in a hard-fought action at Northampton in July.

Margaret fled to Scotland, and Henry was left a prisoner in the hands of the Duke of York.
[Sidenote: Richard claims the crown] The position of York as heir-presumptive to the crown by his descent from Edmund of Langley had ceased with the birth of a son to Henry the Sixth: but the victory of Northampton no sooner raised him to the supreme control of affairs than he ventured to assert the far more dangerous claims which he had secretly cherished as the representative of Lionel of Clarence, and to their consciousness of which was owing the hostility of Henry and his queen.

Such a claim was in direct opposition to that power of the two Houses whose growth had been the work of the past hundred years.

There was no constitutional ground for any limitation of the right of Parliament to set aside an elder branch in favour of a younger, and in the Parliamentary Act which placed the House of Lancaster on the throne the claim of the House of Mortimer had been deliberately set aside.