The Medway Handyman wrote:

I deal with 'difficult' bits with 'spike'
http://www.wickes.co.uk/Builders-Too...ar/invt/167422 or

I've put in all of mine with one of those - and a hand trowel. We're on
sand, with mixed stones and a lot of odd roots. I don't think a borer
would go through, and I've never tried a post spade.

Andy