{{explanation}}
Couples stand in 2 parallel sets facing partners with 1L & 2M, 3L & 4M, 5L & 6M BtoB

1-8
: 1M+3L+6M also 1L+4M+6L dance 1/2 diagonal reels of 3 (1M giving RSh to
  3L & 4M RSh to 6L), 2L+4M+5L also 2M+3L+5M dance 1/2 reel of 3 on
  other diagonal (4M gives RSh to 2L & 3L gives RSh to 5M)
9-16
: 3s+4s dance reel of 4 across
17-24
: All set to partners, 3s+6s also 1s+4s dance 1/2 RH across **while**
  2s+5s change places RH with partner, all set, 6s+2s also 5s+1s dance
  1/2 LH across **while** 3s & 4s change LH with partner (now in order 3
  2 6 parallel with 1 5 4 with 1M+3L BtoB)
25-32
: Middle dancers (1M+5M+4M+3L+2L+6L) dance 6H round & back
33-40
: Middle couples cast to right & dance DoSiDo with partner, all change
  places RH with partner to end on opposite sides 3 2 6 parallel with 1
  5 4