Complex sentence: Under the Constitutional Reform Act 2005, the position of the Speaker of the House of Lords (as it is termed in the Act) became an office in itself, which allowed for the Lord Chancellor to not automatically be the speaker in the Upper House.
Split into simpler sentences: Under the Constitutional Reform Act the position of the Speakership of the House of Lords has become an office in itself. The Act modified the office of the Lord Chancellor, allowing for the Lord Chancellor to not automatically be the speaker in the Upper House.