I’ve got it written down here on a piece of paper

As of June 3rd, some more information on the Register of Members’ Interests
“… as far as volume is concerned there are 7 binders with A4 sheets in them the size of the register grows progressively during the life of a parliament as members must notify ‘alterations of their interests’ within 28 days of the alterations occurring – at present its probably around the 1200-1500 pages but it would keep growing for the rest of the term of the Parliament.”

and a useful bit of history today, again from the Registrar, Bernard Wright (thanks Bernard)
“When the system [Register of Members’ Interests] was put in place in 1984 Members were also required to declare relevant interests orally when speaking in debates, but this requirement was dropped on the grounds that their interests had been declared in writing and that these declarations were public. Some members continue to make oral declarations, and the case you have cited is an example, but these are voluntary.”