What is the point of having a damned robot arm if you can't strap it to a Dalek and send it over to David's to wreak some havok?
I mean, come on! It's not like he's time traveling to get all this stuff done right????????? RIGHT???????????????
OMG!
That's it!
I figured it out!
DavidR8 is Dr Who!
That explains everything. He just pretends he's rebuilt the MGB in a couple of weekends when in reality he has been working on it for the past 20 or 30 years like the rest of us poor mortals and is just now sliding the car through time to make it look like it was only a Tuesday afternoon's work after a couple of pints and a big nap!