In October, Thomas Fairfax, later commander of Parliamentarian forces in the North, signed a pact of neutrality with a Royalist delegation led by his cousin Sir John Belasyse.

[3] When the Second English Civil War broke out in 1648, Francis was a colonel and played a significant role in the campaign that ended with the defeat of the Royalist army at Preston in August.

Lascelles was nominated to the High Court of Justice set up for the trial, as one of the relatively conservative group of property-owning senior military officers known as 'Grandees'.

The Commonwealth ended in 1660 with the Restoration of Charles II to the throne; in April, Francis and his brother Thomas were elected to the Convention Parliament as MPs for Northallerton.

However, in July he and Thomas resigned their seats and went into exile in the Dutch Republic, since Francis was technically considered a Regicide and thus excluded from the Indemnity and Oblivion Act.

Many were condemned to be Hanged, drawn and quartered, while the corpses of Oliver Cromwell, Bradshaw and Henry Ireton were dug up and dragged to Tyburn gallows.

[12] In December 1662, he was accused of being involved in the so-called 'Lascelles Plot,' a conspiracy of former New Model Army soldiers and radicals centred on Northallerton; this proved to be a fabrication by government informers, while the actual Rising in October 1663 quickly collapsed.