Looking at availability just now, it came up with this routing for 150k in First- I got to the point where it said I had a shortfall of 104k miles - but I wouldn't be surprised if it gave it to me had I had enough miles? (was in Oct.)

lhr-cpt-jnb-lhr-nbo-jnb-lhr

the cpt -jnb was same day, as CPT not given as a stop-over.