Public Information Online (PIO) at publicinformationonline.com is an online database provided by Dandy Booksellers, who are well established suppliers of official government print publications. The PIO database collects and provides access to digitised parliamentary papers going back for more than a century.
The material held includes Public General Acts since 1900, House of Lords Papers from 1901, Hansard debates from 1909, House of Commons Bills from 1919, Public Bill and General Committee Debates from 1919, House of Commons Papers from 2006/07, together with more recent collections from the devolved Scottish Parliament, Northern Ireland Assembly and National Assembly for Wales, as well as Command Papers going back to 1955 and non-parliamentary papers such as Law Commission papers, Audit Commission reports and so on. Although some of this material is available in the public domain elsewhere, eg on Parliament’s own website from the start of the 21st century, or via The National Archives, the fact that it can be searched together in one place is a great benefit.
Pepper v Hart
As well as offering general access via search and browse to all this material, PIO also offers its dedicated Pepper v Hart service to assist researches wishing to cite parliamentary material as an aid to statutory construction in court. Essentially, what Pepper v Hart  AC 593 permits is:
“reference to Parliamentary materials where (a) legislation is ambiguous or obscure, or leads to an absurdity; (b) the material relied upon consists of one or more statements by a minister or other promoter of the Bill together if necessary with such other Parliamentary material as is necessary to understand such statements and their effect; (c) the statements relied upon are clear.” (Per Lord Browne-Wilkinson at p 640.)
The Pepper v Hart service harnesses all the parliamentary material on PIO in order to provide, for any particular Bill, a list of all the documents or debates in which it is discussed. It works like this. You select the collection, which will usually be the UK Parliament. Then you select the session, which should be the one in which the relevant bill was passed. Having selected the session, you are given an alphabetical list of Bills or Acts. Having chosen the relevant statute, you are then presented with a list of publications in which it is discussed. Within each publication, you can search for a relevant phrase or quotation.
At this point, you have two options. Either you can open and search within each of the listed documents. Or you can perform a search on all the documents, which will narrow down the list of results, then click on “view selected documents” to display the pages from those documents that contain the highlighted search terms identified. These pages can be removed if not relevant, or added to by adding at any point the next or preceding page. You then have a PDF document, which you can download, containing all the relevant passages to your query. This avoids the need to print out the whole of any document, if all you want is a page or two extracted from it.
There is of course nothing to stop you downloading an entire document and using that for more detailed research. But the advantage of the way the online search works is its convenience, particularly if you are looking for a particular expression in the statute whose meaning is ambiguous or unclear.
While it takes a bit of practice, and works better for some queries than others, there seems to be nothing comparable to this service on any other legal information platform. It cannot be faulted for convenience and ease of use, and I understand that the search functionality is being further developed. (I look forward to being able to use Boolean connectors to conduct more targeted searches, for example.) Even as it stands, I would certainly recommend it as a lot easier and more convenient than the traditional method of scanning all the relevant printed materials by hand.