BR built just 20 Ferry Tubes - similar in dimensions to the standard tube, including corrugated end, but with two drop doors and full air brake rigging. Later they were popular with engineers, including carrying railway spares on the ferries to Europe. 4mm drawing in Model Railway Constructor Annual 1984 pp 111-118 & Bartlett et al BR wagon book.
![21 70 609 4 046-7 ZDX Ferry tube @ Dover 87-05-30 [1]](/img/s/v-10/p121368902-11.jpg)
![21 70 609 4 049-1 ZDX Ffs Ferry Tube Diag 1-449 @ Hoo Junction 82-11-06 © Paul Bartlett [1w]](/img/s/v-10/p99047976-11.jpg)
![21 70 609 4 049-1 ZDX Ffs Ferry Tube Diag 1-449 @ Hoo Junction 82-11-06 © Paul Bartlett [2w]](/img/s/v-10/p428572979-11.jpg)
![21 70 609 4 049-1 ZDX Ffs Ferry Tube Diag 1-449 @ Hoo Junction 82-11-06 © Paul Bartlett [3w]](/img/s/v-10/p389961592-11.jpg)
![21 70 609 4 049-1 ZDX Ffs Ferry Tube Diag 1-449 @ Hoo Junction 82-11-06 © Paul Bartlett [4w]](/img/s/v-10/p504415925-11.jpg)
![21 70 619 0 051-0 OIX Ferry tube @ March 78-06-28 [1]](/img/s/v-10/p169049093-11.jpg)
![21 70 619 0 051-0 OIX Ferry tube @ March 78-06-28 [2]](/img/s/v-10/p44437643-11.jpg)
![21 70 619 0 057-7 ZDX Ferry tube @ Dover 87-05-30 [1]](/img/s/v-10/p16600459-11.jpg)
![217060 940533 ZDX Ferry tube @ Dover 89-01-15 [1]](/img/s/v-10/p257014656-11.jpg)