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 almost 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 treat them as standard. CF'84 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. (For instance, the Metropolitan line between Baker Street and Aldgate, and the Hammersmith & City line up to Barking were changed to run at standard London Underground hours, with the stations closing at around 11:00pm.) The closure of several stations affected things a little more – in particular there are far fewer Amersham-Aldwych loops now Aldwych is a ghost station, and the Ongar Denial is no longer as easy a way out of a Dollis Hill for the same reason. However, when the ghost station rules were applied, neither of these changes required a rewrite of the rules as a whole.
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 four, and the ruleset proved too inflexible to cope. The general answer from the IMCS has been to consider the DLR an honorary rather than actual part of the Underground, somewhat like the North London line, and bring the Jubilee extension under the foetal station rules. However, many players' committees did not accept this change, and have proposed various amendments to bring both the DLR and North London lines into the fold, some of which have been accepted by the IMCS (but none by CAMREC.) Unfortunately, none of the amendments has been completely bug-free – for example, the 1997 set generated a loop around [Leicester Square]? (!). Perhaps the most successful amendment was the Finsbury Option amendment of 1988, which introduced a fifth 'quadrant' to hold the Jubilee extension and the Docklands Light Railway. This amendment was used successfully on the York MC server until its closure.