Thanks for the responses all.

Unfortunately the reason they are separate itineraries is because one is Amex 2for1 voucher redemption in First, and the other is a business trip which was booked at a later date.

Worst case scenario, I will miss the last flight out to Madrid and hope that there is availability on the first flight out the next morning.

If the Moscow to London flight is running late, at least I'll be delayed in style.

Thanks,
K