Erskine May - the "bible" of Parliamentary procedure - is now available to read for free and in full online for the first time.
The book is the go-to guide for anyone in British politics and is often referred to by Speaker John Bercow.
Previous editions had only been available in print - with the most recent publication priced at £329.99.
Parliamentary authorities have also confirmed that future updates to the book will be available online.
The newest edition - the 25th - is now on the parliament.uk website and is fully accessible and searchable.
Mr Bercow said he was "delighted" at the development, adding that "Parliamentary practice and procedure does not exist in a vacuum."
The current Clerk of the House of Commons, Dr John Benger, said Erskine May "attracts wide public interest as a source of information and is also influential in many other countries".
"The digital version will maintain the iconic status of Erskine May whilst opening up parliamentary practice to a wider audience, something that is all the more important at this time of such great constitutional and procedural turbulence."
The first edition was published in 1844 when Erskine May was Clerk of the House.
The most recently-published edition is the 25th print.
What changes have come in since the last edition in 2011?- Here are a few of snippets from the new online version:
- English votes for English laws - introduced in 2015, this means some laws which directly affect England and Wales can only be voted on by English and Welsh MPs
- Fixed Term Parliaments Act - enacted in 2011, means Parliament must sit for five years unless two thirds of MPs vote for an early general election
- Recall of MPs Act - established in 2015, allows for a constituency to recall an MP for misconduct in office
- Creation of e-petitions - started in 2011, allows for ordinary citizens to raise topics for debate in Westminster Hall. At 10,000 signatures the government responds, at 100,000 the petition is debated in Parliament
- Changes to UK law as the the country continues with its planned exit of the European Union