* The TES front-page story reveals unprecedented numbers of A-level papers have been downgraded this year because initial results were too high. Schools complained of a results "fix". The claims focused on Cambridge board OCR.
* The Government's exam watchdog launches an inquiry.
* The Headmasters' and Headmistresses' Conference, which represents private schools, says that a fifth of its 246 schools have been affected by "bizarre" results.
* OCR's chief executive Ron McLone agrees to meet HMC leaders on Thursday.
* The Qualifications and Curriculum Authority continues its investigation but claims the awarding process is sound.
* HMC says it will support legal action against OCR unless the A-level results are explained.
* The Prime Minister's official spokesman says it is "utter rubbish" to suggest that the Government asked the exam board to downgrade pupils.
* Headteacher associations call for an independent inquiry into "fixing" allegations, claiming the QCA is too involved with the exam boards.
* QCA asks OCR for coursework and exam results in English, physics, chemistry, history, geography, design and technology, French, German and psychology.
* The QCA's new chief executive Ken Boston appears on BBC2's Newsnight. He denies suggestions that the quango instructed boards to depress grades.
* Mr McLone is also interviewed on the programme. He insists that OCR has followed the rules and says teachers have failed to appreciate the harder demands of the A2 assessment.
* Sir William Stubbs, QCA chairman, and Ken Boston called to the Department for Education and Skills.
* A stream of state and independent schools come forward with grade concerns. Some relate to AS exams and also to boards AQA and Edexcel.
* Sir William denies the exam boards were under political pressure to downgrade marks.
* Headteachers' demand ministerial intervention.
* OCR confirms TES revelation of 11th-hour grade shifts but denies any wrong doing.
* More examples emerge of students who have lost university places because of U grades.
* Demands are made for a ministerial appointed inquiry into the whole exam system.
* The Government annnounces that thousands of entries are to be re-marked.
* HMC, the Girls' Schools Association and the Secondary Heads Association set to demand the restoration of original boundaries and the re-issue of results.
* QCA due to report its findings to Education Secretary Estelle Morris.