That's odd. The Haynes book was written by David Fletcher, who most certainly knows about the alleged grapple in the Tank Museum, and yet the photo chosen for the book shows a four-armed (four-tined?) device. In the book, you can see the shackle that was an integral part of the design; it was supposed to spin so that it would twist the wire up. There is also a photo of a tank using a grapple, and although the grapple can be clearly seen it isn't clear how many tines it has.
Hello
There was at least 2 models
1 with 3 flukes ( As in Bovington's museum)
1 with 4 flukes ( Found on cambrai's battlefield , still with his 2 shackles)
There is a picture of the 4 flukes model in Gorzinsky- Gibot ' s book " following the tanks"
Also a less good picture of this one in the book " Le triomphe des tanks a Cambrai"
Best Regards
Olivier
