His uncle was a Fellow of Peterhouse at the time and when his uncle lost his post due to his Royalist views, Barrow went to Oxford where his brother had become the King's Linen Draper. However there was an uprising against Royalty and Oxford came under siege. In 1644 Barrow went to London where he was supported by Thomas Fairfax.
Kanyang tiyuhin ay isang Fellow ng Peterhouse sa oras at kapag nawala ang kanyang tiyuhin sa kanyang post dahil sa kanyang mga royalista views, Barrow napunta sa Oxford na kung saan ang kanyang mga kapatid na lalaki ay maging ang hari ng de ilo Draper. Subalit nagkaroon ng isang pag-aalsa laban sa pagkahari at Oxford nagmula sa ilalim ng paglusob.