system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did the English crown lose all of its power to a modern form of government?
gpt
Well in 1215, King John of England signed the Magna Carta, which stated that his will was not law, meaning that a man couldn't be punished because the King wanted him to be, he had to have done something that went against the law of the land. This was the first step towards a modern form of government. 

Henry III was the first Monarch to call parliament (first recorded occasion of them being called) in 1236. Edward I, who reigned 1275 - 1307, then began to call parliament frequently, and, along with calling noblemen and churchmen, also issued orders for the elections of one representative from each county (knights of the shire) and two from each city (burgesses). This set the precedent for parliament to comprise of three aspects; the commons, the lords and the monarch (which remains the same to this day), although their main concern was primarily to consent to or decline the taxation the King suggested.

During the 14th century Edward III stated that parliament should meet annually, and their increased activity lead to them becoming move involved in issues other than the King's taxation wishes. In the late 14th century the parliament became more powerful and started having influence over the King's ministers and Lords, forcing corrupt ministers to step down, and by 1399 they were so powerful they forcefully removed Richard II as King. After this the commons held a very powerful position, and managed to secure an equal role in lawmaking in order to secure a deal with future king Henry IV. 

Henry VIII then affirmed parliament's power around 1529, because he gave them the power to remove the pope as head of the Chruch in England and replace him with the Monarch. This meant that Henry VIII was head of the church, but also left parliament even more powerful. The civil war of 1642 - 1651, which resulted in the temporary abolition of the Monarchy, further proved that the King was not all powerful, and the restoration of the Monarchy was done with the people's consent, meaning that the Monarch was aware that parliamentarians were capable of overthrowing him if he acted in an unconstitutional way. 

Further limitations to the power of the crown were:

- Bill of Rights 1689, which guaranteed freedom of speech in Parliament, a right to petition the King without fear of retribution and regular elections to parliament. 

- Habeas Corpus act 1701, which meant courts had to examine the lawfulness of a prisoner's detention. 

- the Petition of Rights act 1860 that set out liberties of the people that the King was prohibited from infringing. This included unlawful taxation, use of the armed forces for unlawful means and infliction of martial law, amongst other things.