The now perennial Helsinki Tier Point run is back again at the very sweet price of £195, equating to £1.22/TP.
There is one catch however. Assuming you want to return to your start point, the minimum stay is 4 days. However the ticket price is the same in both directions (i.e London-Helsinki return is the same price as Helsinki-London return), and it is permitted to nest tickets.
The fare is available for travel until May 2020, but available dates are quite sparse for the London-Helsinki-London direction (see below image), so you need to play around with return dates a little bit. Check over at BA's Low Fare Finder.
Availability is a bit wider in the Helsinki-London-Helsinki direction, as below.
While you're in Helsinki Airport, you should review Finnair's newly-renovated business class lounge near Gate 50.
Book over at ba.com.