In the beginning of 1455, he was appointed to serve on a commission to arbitrate between the Duke of York and the Duke of Somerset, the failure of which was shown in the first battle of St. Albans in the following May. Later on, apparently in 1460, before the battle of Northampton, he again took part in an attempted reconciliation of the Yorkist leaders. At length, on 25 October 1469, he was made Lord High Treasurer, and held the seals until the following July. Grey's tenure as Lord High Treasurer occurred during the Great Bullion Famine and the Great Slump in England. On 26 August 1471 he was named first on a commission of fifteen to hold a diet at Alnwick to deal with the infractions of the truce with Scotland, and in the following March to treat with the Scots ambassadors at Newcastle-upon-Tyne on 25 April, and again on 16 May he was entrusted with a similar negotiation.