Michelle O’Neill, the Sinn Fein first minister, has pledged to ensure the stadium is built and said on Sunday: “The next time a ball is kicked for the European Championship, it could be in Casement Park.”
The report of Mrs Gray’s involvement sparked anger among unionists on Tuesday night, with prominent loyalist activist Jamie Bryson saying: “If the GAA – a nationalist organisation – are to get hundreds of millions more than was agreed, then what is the unionist community getting of equal value?
“For decades nationalism have got got got, and unionism has give give give. The time to draw a line was long ago.”
The Prime Minister vowed to “resolve” Casement Park’s funding issues after visiting Northern Ireland last week.
“A number of issues were discussed this morning and as you would expect, finance came up, the health service came up, Casement Park came up,” he said in Stormont.
“We addressed those constructively. I understand the case in relation to investment and financing in particular. We will work to resolve those issues constructively.”
Sir Keir is due to meet Simon Harris, the Irish Taoiseach, at Chequers on Wednesday.
Gray’s connections to Northern Ireland
In the 1980s, Mrs Gray ran a pub with her husband Bill Conlon, a country music singer, in the border town of Newry, south of Belfast, at the height of The Troubles.
She has twice had to deny claims that she was a spy, telling both the BBC and Sir Keir’s biographer Tom Baldwin that they are untrue.
Mrs Gray later returned as permanent secretary of the Department of Finance in the Northern Ireland Executive in 2018, before returning to Whitehall in 2021.
The stadium was built in 1953 and named after Roger Casement, the republican revolutionary executed for his part in the 1916 Easter Rising against Britain.
Windsor Park, where Northern Ireland usually play international matches, is too small to host Euros games because it only has a capacity of 18,500.
No 10 and the Cabinet Office were approached for comment.