The government is expected to announce a U-turn on A-level results at 4pm this afternoon.
All A-level and GCSE pupils in England will get teacher assessed grades, rather than the standardisation process which has come under heavy criticism.
Boris Johnson has faced mounting pressure from within his own party this week as senior Conservatives called for the Government to resolve the “shambles”.
The Prime Minister has gone on holiday to Scotland this week despite the chaos over the A-level results, but held talks with Mr Williamson and senior officials on Monday morning.
In an indication that the grades awarded last week may not be the final results, a Number 10 spokesman said “the Government continues to work hard to come up with the fairest system possible”.
Defence Minister Johnny Mercer said he was “acutely aware of the issues around A-level results and am equally concerned for the GCSE results on Thursday”.
In a hint that a U-turn was coming, he said: “I do not believe this is the end of the story – there are too many clear injustices.
“At this time we must not panic, and await developments. I am limited in what I can say publicly – I have had many private conversations.”