Originally Posted by Confus

One PNR and one ticket, then yes absolutely.

However, don’t worry about the naysayers (in this instance anyway). Russia is not some third world tinpot hole, it’s a modern transport hub with clear and transparent transit rules - and these particular rules haven’t changed for quite some time now. You are permitted 24 hours airside transit in the same airport (from a given list, but DME is there) if travelling to a third country, and won’t have any trouble at all from BA check-in or the Russian authorities as long as you have proof of onward connection.

The absolute worst that might happen is having to stay ages in a boring airport terminal. No different really from all those who transit UK/other European airports every day with no right to enter en route.