You may already have seen the entry on the English Civil War, which also touches lightly on some of the causes. This entry explains the events which led up to Charles I raising his standard in 1642...
Lack of Money
One of the reasons why the civil war broke out in England in 1642 was because of Charles' lack of money. To discover the source of this, we have to go back to the beginning of James' reign.
James was the first King to reign over both England and Scotland, and when he came down from Scotland it is said that he was astonished at how rich England was, while James had needed to borrow money for his travelling expenses. When James died in 1625, Charles came to the throne, and he, like his father, had very little money. Once Charles became King, the County Faction1 wanted him to go to war with the Catholics in Spain, so Charles asked them for taxes to use on the war. They refused to pay enough, so the war was hopeless, and Parliament blamed the King for this.
The reason Parliament granted so few taxes was that they wanted to make sure they were called again. Charles, a firm believer in the Divine Right of Kings, thought that he should not have to rule with Parliament, and the only thing that kept him calling it was money2. One good example of the way Parliament made sure they were called back in Charles' reign was tonnage and poundage. These were duties imposed on certain imports and exports. It was normal for these duties to be decided in the first Parliament of a monarch's reign, but in the case of Charles, they only decided on it for one year, so the King would be forced to call them again. Although Charles tried to ask for more money, Parliament refused, because they believed he spent it on his favourites. Because of this, Charles had to get himself more money. He began using the Church Courts, exploiting taxes such as 'ship money'3, and selling monopolies and titles. He also opened a Court of Star Chamber, which he used to fine people heavily to raise money. Since the judges in the Star Chamber were officials of the Crown, and there was no jury, Charles could be sure of getting a favourable result. Parliament was furious with this, and immediately drew up the Petition of Right, which asked the King to stop illegal taxation. The King signed it, but only because Parliament threatened to impeach Buckingham, one of the King's favourites.
The quarrels about money went on, and eventually Charles decided to dissolve Parliament. He reigned without them for 11 years. When the new prayer book was brought into Scotland, a group called the Covenanters attempted to invade England. Charles called a Parliament to try and get taxes to fight the Covenanters, but they refused4, so Charles dissolved them again. He was forced to pay the Scots £850 a day to stop them advancing, and eventually, in 1641, his money ran out, and he had to call Parliament - he was bankrupt and at their mercy, so money was definitely a key factor in the outbreak of the civil war.
Another major influence in the outbreak of the civil war was religion. The religious quarrels began right at the start of Charles' reign, when Charles married Henrietta Maria, a French Catholic. Although Charles didn't choose to marry her - his father, James, set up the marriage - the public, especially the Puritans, didn't like having a Catholic as Queen. A few extremists even saw this as a sign that Charles was secretly Catholic! After the King dissolved Parliament, he made William Laud the Archbishop of Canterbury, in 1633. While Laud was Archbishop, he made many changes to the Church. Most of these changes involved beatifying the Church and bringing back robes for priests, statues and stained-glass windows. All these things reminded the English of Catholicism.
In 1636, Archbishop Laud decided to introduce the English Prayer Book (which stated how services should be run) into Scotland. There was nationwide rioting, because no one wanted to follow the new Prayer Book. Scotland was a Presbyterian (Puritan) country, and they thought that the English Prayer Book was far too Catholic to use in Scotland. This eventually led to many Scots, called the Covenanters, marching down the country in an attempt to invade England. At this point, Charles had to call Parliament to ask for taxes to pay for the war, but was horrified to see that most of the MPs were on the Covenanters' side. Parliament agreed that the Prayer Book was too Catholic, so Charles dissolved them again, but after he ran out of money to pay the Scots (see the Money section above) he was forced to call Parliament again.
Parliament first put Laud on trial, and found him guilty. Later they decided to execute Strafford on charges of organising an army in Ireland, where he governed. It turned out that this was a big mistake. As soon as Strafford was executed, the Irish Catholics rebelled against the Protestants, saying they were rebelling for the King. Although it was clear this was not true, Parliament did not trust the King when he asked them for an army, and so refused, believing he would use it to crush them instead.
Another factor in the outbreak of civil war was foreign affairs. On the continent, the 30 Years War was going on, where Catholic rulers attempted to wipe out the Protestants in their countries. This fuelled people's fears that something similar might happen in England. Other foreign causes of the war were from Ireland and Scotland, and are detailed above.
Although it may seem unimportant, Charles' personality was a major factor in the events leading to civil war. To start with, Charles hadn't expected to be King at all - his elder brother, Henry, had been expected to take the job, but when he died suddenly in 1612, Charles became the heir to the throne.
Charles also believed in the Divine Right of Kings. He thought, as his father had before him, that Kings were appointed by God, and could not be wrong. He disliked having to rule with Parliament, and thought that he should be able to do anything he liked. This caused much friction between him and the MPs.
The Short Parliament
When Parliament was summoned in April 1640, Charles had governed for eleven years without them5, and while this certainly went against the spirit of the English constitution, it was within the King's prerogative to do so. Charles was forced to call a parliament when the Scots rebelled. Putting an army into the field to deal with the Scots put a heavy drain on the royal finances, so Charles needed to levy a tax, which he could only do with the consent of Parliament.
When Parliament met the gentry from the counties used the occasion to vent their frustration, with Harbottle Grimston and John Pym leading a catalogue of complaints. Three weeks later, Charles dissolved Parliament, blaming 'the malicious cunning of some few seditious affected men'. This was known as the Short Parliament and it sat from 13 April, 1640, to 5 May, 1640.
The war with the Scots did not fair well for Charles, but he eventually came to an agreement of £850 a day to keep the Scots at bay.
The Long Parliament
In order to pay this and get funds for a final settlement Charles had to summon another Parliament6. This time Charles could not afford to dismiss Parliament until he got what he wanted, and this gave Parliament an important card to play in what was to come. The Long Parliament, as it was known, sat from 3 November, 1640, for 13 years, until Oliver Cromwell suppressed it. It should be noted it was not formally dismissed until 1660, after the Restoration.
Therefore, when Parliament met in November 1640, it was with a mood of constitutional reform. Of the 493 MPs elected:
340 were anti-Court (the County Faction)
64 were for the Court (supporters of the King)
59 were of an unknown disposition
17 were disabled from sitting (these were mainly of the 'Court Camp')
The remaining 13 were probably of the Court Faction.
Parliament pinned the blame for what went wrong on the King's advisors, rather than Charles himself, sending both Strafford and Laud to the Tower. Charles also tried to heal the rift by signing Strafford's death warrant, passing a bill that allowed for Parliament not to be dissolved without its own consent, a bill making 'ship money' illegal and other bills that taken together demolished the framework of prerogative government.
The Thrilling Climax
All of these causes led to some key events in 1641 and 1642. It turned out that the execution of Strafford had been a mistake. Without Strafford to reign over Ireland, the Irish rebelled in 1641.
This raised an insoluble problem; who would command the Army, King or Parliament? John Pym took the initiative by issuing the Militia Bill and, more importantly, the Grand Remonstrance. It listed all the things Charles had done wrong in his reign, suggested less power for bishops, and said that Parliament should have power over the Church and the appointment of Royal ministers. It was passed by 11 votes, which meant that, while most of the Commons had previously been against him, now almost half of them supported him.
However, it was after this that the King made a foolish move. On the advice of his Queen (who was used to French politics, where the King had much more power over the way the country was run), Charles decided to arrest the five ringleaders, including Pym. On 4 January, 1642, Charles attempted to get into the Commons to arrest the five MPs, and found that after he and his guards had battered the door down, the MPs had been warned and weren't there. This action turned most of Parliament against him once more, because it was held to be a breach of Parliamentary privilege7. On the next day, the escaped MPs paraded up and down London guarded by the Trained Bands, an army of part-time soldiers. After this, Charles fled to Nottingham, and it was there, on 22 August, that he raised his standard, marking the start of civil war.
1 It is traditional to refer to the two factions in Parliament as Court and County; Court were effectively in the King's pocket, and County were MPs who tried to represent the views of the landowners.
2 Since the Magna Carta, no monarch could raise taxes without Parliament's permission.
3 'Ship money' was a duty imposed on sea ports to pay for the upkeep of ships. Charles I extended its use to other towns.
4 Most of Parliament actually agreed with the Covenanters, and they believed the King should have enough money of his own.
5 This became known as the Eleven Years Tyranny.
6 The main sources for this section are The English Civil War by Robert Aston, Fidelity & Fortitude by Martin Hazell, and The Oxford Illustrated History of The British Monarchy by John Cannon and Ralph Griffiths.
7 So much so, in fact, that a shout of 'Privilege! Privilege!' went up as the King prepared to leave.