How, when and why was the description of the all-round/diamond poussette changed to the present wording?

Answer :

The first description of this formation is given in the dance New Park in book 19, (1957) but it involves 1^st and 3^rd couples dancing, while 2^nd couple stand still on the sidelines between them.  The diagrams certainly indicate that the two couples dance straight in towards each other to start, finishing angled diagonally, but not in the same diagonal line, at the end of bar 1.  Book 19, however, did have a large number of errata and corrections to many of the diagrams.  This formation became known as the “diamond” poussette.

 '99 More Scottish Country Dances' was published in 1963. In it Miss Milligan describes the strathspey poussette, with diagrams, pretty much in line with the current RSCDS Manual description.  It shows very clearly 1^st and 2nd couples in the same diagonal line during bar 1.

In 1968, in “Introducing Scottish Country Dancing”, Miss Milligan gives a more detailed description of the formation, “On 1, first and second couples dance into a diagonal line from second lady to first man – first lady and second man back to back in the middle.”

  
Both editions of the Manual have followed the descriptions set out in 1963, 1968 and 1976 as the basis of the current wording.