It is 86246 and it is there as a spares donor. It won't be re-entering service.
It's kept Les on the tracks with its bogies.
After completing the 2014 'heritage' trips, 86259's wheels were deemed life-expired. I recount elsewhere the trials and tribulations endured in trying to find a practical and not-horrendously-expensive way out of this problem. The eventual (and probably only) solution resulted in the acquisition of 86246's bogies from Europhoenix on terms that just its wheelsets would be swapped for those of 259. 86246 was destined to be a donor for spares for the Electric Traction fleet and, since the bogie frames and traction motors of 86259 were perfectly serviceable, a swap of the wheelsets would leave 246 capable of being mobile.