The message
from James Fidell contains these words:

In article , Dogger wrote:

My allotment hasn't been used for about five years. I dug it over last
year and it was like digging over the Gatwick runway.

I was thinking of getting one of those mantis cultivatiors. Any one
got a view on them?

I know a couple of people who have one and think they're great, but
their ground is already fairly well cultivated. The veggie garden
I'm working on at the moment on the other hand, which has been pretty
much ignored for perhaps as much as ten years, was almost completely
untouched by quite a heavy duty rotorvator, so the mantis would
certainly have been pointless.

James

This one`s been dug over once so it should be a little bit better. Must
admit I`d rather have a big brute for the big work but the Mantis looks
useful for preparing seed beds and weeding.

The OP could of course hire a big one for the times he needs a big un.