I thought that Hugh Piggot uses at lest 2" (60.3mm) pipe for the top of the tower. And, if you calculate the fact that if we double the diameter (with the same wall thickness), we get 16 times the strength of a pipe, it's wise to do so. It means that if we enlarge the pipe for 30%, we get more than five times the strength.
Also, be careful with constructing the tower. In my area, I saw many such constructions failed. It's not always a bad weld, it's difference in material structure, temperature expanding etc. And, mostly those micro-vibrations that are hard noticeable, but very destructive.
The option with one pipe fixed in the earth, in concrete, is good (supposed the base is OK), but I wouldn't go with just the bolts when connecting the main tower pipe and the fixed one. A kind of a bushing thru the both pipes is recommended, for stronger connection. And tight connection, to eliminate vibrations.
Vibrations are like wood worms. They go all around ant searching a place where they can make a damage.
I prefer lattice freestanding tower, because I can find the material for free. Right now i'm building two sections 20' each. It's straight-width tower, with lot of bolts and profiles, oversized bit. (That's the main reason I'm happy).
Anyway, good luck with your project. And remember: Any anchor-diameter is better than none. It's better to put the guy wires on the 3m diameter from the tower base, than to go without them.