You think it's feasible he killed her, had a whiskey, wrapped up her body, loaded it into his Land Rover, drove to the pub (where according to one report he spent the evening, but let's play it your way and say he only stayed for one), drove back to his farm where he drove around his 276 acres looking for a suitable spot to bury her, got out, dug a hole, and then took her out of the Land Rover all within the space of less than an hour do you? He must be the same sort of super human speed as Gerry then, yar?
Good evening Alf.
I would imagine he was pretty familiar with the farm so driving around searching would not come into into the equation, he would know. A competent digger operator would open up a trench shove in the body and backfill in about ten minutes; fifteen minutes top whack.
How big do you think 276 acres is? (how big's a cubit anyway?). It would have a perimeter of about 4km so how long to drive round that? At 15kph that's about say 15 minutes. Even assuming he went the long way round the farm that still leaves 30/35 minutes to drive to the pub and have a quick one and so on. He wouldn't need to be greased lightning exactly.
Just saying like

Before you ask I am not saying anything other than he would be familiar with the farm; 15 minutes; 4km;15 minutes; residual time 30 minutes minimum.