In its day, the set of rules drawn up by the IMCS and Mrs Trellis in a meeting at Chalk Farm, in 1984, was regarded as the greatest of its type. It was intended to be the standard ruleset for all MC everywhere, and was very nearly totally successful in this aim. Indeed, even now there are many who hold to these as being the most consistent, straightforward and fair rules ever written down, and many MC tournaments and clubs still regard this as standard. It is also the only ruleset of recent vintage to have been accepted by both CAMREC and the IMCS.
However, in recent years there has been a tendency away from Chalk Farm '84 on the grounds that it no longer reflects the reality on the Underground, as several changes have happened to the network since then. The creation of the Hammersmith & City line as a separate line (it was formerly part of the Metropolitan) did not unduly affect things, nor did the changes to the various peak-hour schedules (Metropolitan between Baker Street and Aldgate, H&C up to Barking now being all-hours times). The closure of several stations has affected things a little more - in particular there are far fewer Amersham-Aldwych loops now Aldwych is a ghost, and the Ongar Denial is no longer as easy a way out of a Dollis Hill for the same reason: but, with ghost station rules applied, these did not require a rewrite.
Of greater concern was the long extension to the Jubilee Line, and the admission of the Docklands Light Railway to full Underground status. This seriously unbalanced Quadrant 4, and the ruleset proved too inflexible to cope. The general answer from the IMCS has been to consider the Docklands an honorary, rather than actual part of the Underground, somewhat like the North London line (under Chalk Farm rules anyway), and bring the Jubilee extension under foetal station rules. However, many have not accepted this and have proposed amendments to bring both the Docklands and North London lines into the fold, some of which have been accepted by the IMCS (but none by CAMREC). But none of the amendments has been completely bug-free - the latest 1997 set had a notorious Leicester Square loop. Perhaps the most successful amendment was the Finsbury Option amendment of 1988, which brought in the theory of Quadrant 5 to hold the Jubilee extension and Docklands (and was used on the York MC server until its closure).