Apart from it probably being an offence to drive on the right hand side of the road in this case (lawyers let me know), it's still highly dangerous. 1) The Audi didn't indicate before they started to overtake. 2) A vehicle in the left lane could have wanted to turn into that side road (where the Audi eventually did) and suddenly pull out. 3) A vehicle could have suddenly pulled out from the side road the Audi went down. 4) Pedestrians on the right pavement may have wanted to cross the road, and would not necessarily expect a vehicle to be driving from the left. towards them.
