It seems there's nothing some people can't, or won't nick. Quite a few people have turned to military barriers to keep the blighters out (provided by Sanderson... check it out here).

What's the best object to block a gateway? (That they won't nick for scrap)

oliver.mark:

What's the best object to block a gateway? (That they won't nick for scrap)

Wet Hesstons off the top of the straw stack. Easy to shift with a muck grapple, impossible any other way!

did a deep hole, and fill it with slurry!

A narky Frisian bull would probably be the best thing to keep them out, but it would probably keep you out too, hesstons would be a good one but it seems they are getting more nasty lately and if they cant steal what they want they will vandalize or burn everything incite just to spite, In the past we have welded some heavy brackets onto a sturdy metal (rsj) concreted in post, with an RSJ going across the front of the gate,(but it would need to open outwards or the gate is weak if ramed) with a good lock so you can open it like you would a gate to get in,obviously it would need to be high enough that if they attempt to ram it, it will be above the bumper,(ideally taking out the radiator) but this can take a bit of time to make up, which most of us dont have,

 Quarries can supply you with a few really big, five ton plus boulders. They're solid, low value, won't burn and once set can't be moved. On the downside, once set they can't be moved. Even by you!

Landmines? Or are they illegal????

Just an upturned set of chain harrows buried in the grass would stop them. Just remember they are there yourself!

two or 3 of those 1000 litre plastic tanks filled with concrete work well

best deterrent for gypsies is big dung middens everywhere