The Benbo tripod is a truly amazing piece of kit for the natural history photographer! I bought mine, an original Benbo Mk I made by Kennett Engineering, in the mid-1980s. It has served me well and the only maintenance it has required has been occasional greasing of the tightening mechanism and replacement of one of the rubber feet (which split). I think I was influenced to buy it by Heather Angel's recommendations, for example in her "Book of Nature Photography". She appears in a video demonstrating it on YouTube.
The legs and central column of the Benbo are joined by a bent bolt which allows the legs to be moved out at unlikely angles. The name "Benbo" apparently comes from the initial letters of the words "bent bolt". The idea is supposed to have come from the tripod designed for the Bren gun in WWII.
It is a big, heavy, solid tripod equipped, as you can see, with a hefty ball-and-socket head. So it is not something I like to carry for any great distance, but provides very solid camera support.
If you want one, you need to know bit of history: The Benbo was original made by Kennett Engineering, a small company set up by two engineers, Chris Mills and Ken Brett, in Leighton Buzzard in the West Midlands. They eventually produced a whole range of Benbos from Mk I to Mk. VII, with the higher numbers generally being bigger and heavier versions (except for the small and light Mk VII). The Mk V was huge weighing in at 22lbs and extending to 10ft! They eventually sold out to Paterson Photographic based in Tipton, also in the West Midlands who still make Benbos - although the design and manufacture has changed (some say cheapened!) over the years and most of the parts are now made elsewhere and just assembled in Britain. The current range includes the Mk I and bigger Mk II, but also includes a smaller, carbon fibre versions (Benbo Trekker) based on Kennett's Mk. VII. But, once the "non-competiton" clause of their agreement with Paterson ran out, Chris and Ken started a new company, Uni-Loc Tripods, in Leighton Buzzard making an updated version of the same design. There is a brief account of this here. They eventually sold out to "Envoy" who still market tripods under the "Uniloc" name from a base in Herts.
So, you can consider the current Benbo models from Paterson Photographic or look at the Uniloc range from Envoy.