The History of the Rebellion and Civil Wars in England Begun in the Year 1641
Edward Earl of Clarendon
Late Lord High Chancellor of England, Privy Counsellor in the Reigns of King Charles the First and Second
Published in 1707, and written by someone who not only experienced the civil war, but who held a high position at the time.
From the preface:
"This history was first begun by the express Command of King Charles the First, who having a desire, that an account of the calamities, God was pleased to inflict on the unhappy part of his reign, should be reported to posterity by some worthy, knowing and honest man, thought that he could not appoint anyone more adorn'd with such qualifications, than this author."
What more can we say? Apart from the fact that this is the original account of the English Civil War.