So the best tool goes to the Bulldog all steel Grafting Tool. When the clay's right you can dig very quickly with one of these. They have a nice heft so you can throw it down to cut deep into the clay and it doesn't bend when leveraging nice large chunks of clay.

We ended up digging by hand because we couldn't get a big enough mini-digger. It would have needed to be large enough to stay well back from the edge of the hole while still being able to dig over 2 m deep.

I'm glad we dug it by hand, thanks in part to the good weather. It was a good decision from our engineer (saved us time and money) and the size of the holes was perfect (800 x 1400 mm). The clay was firm, the holes held their shape (in fact we had one open down to 1500 mm for a week) apart from the mishap below and we didn't need shoring. We also dug and poured both pads at once.

The only problem we had was hitting an old field drain. Water seeped in over night and it ruptured the side of the hole a couple of times until we fixed it properly.
http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=10524

First stage done! - looks less scary than the drawings :)

Hallelujah, slab poured! Clayboard was a pain and the steel reinforcement was outrageous but we got there in the end. Rained last night before the pour and despite covering Clayboard in plastic and over top with a tarpaulin a little dampness still got in, so very glad to see slab in place and not going any where!

LOL, indeed!

Shevek

I am a little disappointed you have not even worn the paint off that bulldog spade.