This website allows you to quickly and easily search more than 1.6 billion words of text, in more than 7,600,000 speeches from nearly 40,000 individual speakers in the British Parliament from 1803-2005. You can search for words, phrases, collocates (nearby words), and even grammatical constructions. You can also search the corpus "semantically", when you want to find all words with a particular meaning.
For any of these searches, you can see the frequency over time (1803-2005), either by decade or by year. You can also compare one set of decades to another. You can quickly and easily create "virtual corpora". These might include just the speeches of a certain member of parliament (or a group of MP's), perhaps during just a specific time period.
The corpus was created as part of the SAMUELS project (Semantic Annotation and Mark-Up for Enhancing Lexical Searches), 2014-2016. The corpus architecture and web interface was created by Mark Davies, and it is related to other large corpora of English.
The 5-10 minute introduction provides a very good overview of the main different types of searches that one can do. We invite you to start with that web page, if you haven't done so already.