Sadly, Captains operating in the RHS has been normal in most of the UK charter airlines for many years.
It is becoming more common in UK airlines by the year as the CAA are too weak to stop the process. easyJet are not being original in their actions only copying what the others are doing.
It is a totally unsafe practice which should never be allowed as the Captains are not line trained or checked in the seat. They can be called to operate on standby having not been in the seat for over a year or two. The only requirement is that they do the mandatory engine failure scenario in the sim every six months...very useful as they are not allowed to fly from the RHS when they are there...unless it's a Cat3 approach when they get to twiddle the autopilot from the wrong side.
When you consider that the CAA have been allowing this for years it is a shamefull concession to commercial pressure as our airline is now, like most, using RHS Captains to make up for the loss of FO's to carriers that don't stoop to such low levels of desparate crewing.