I recall reading here many months ago that BA had introduced discounted one way fares between LON and selected Euro Zone 1 cities. Unfortunately, search has let me down today as I've not been able to plug in the winning search terms to retrieve the thread in question.

I discovered today, purely by accident, BA.com offering one-way R class fares from a variety of European cities to London, eg.

TXL-LHR EUR212 (~£185)
PRG-LHR 6660CZK (~£215)
FCO-LHR EUR222 (~£195)
ATH-LHR EUR263 (~230)

Similar one fares are quoted ex LHR. When making one-way reservations for travel in economy class, BA.com also offers the proactive option of upselling to R class (but not I class as far as I can make out). For those of us living outside of London, BA.com combines R class with Domestic J class for one-way travel to/from UK outstations. The one-way CDG-EDI booked this afternoon priced out at a very respectable EUR 248, which was a mere EUR 80 higher than the prevailing restricted ET fare.