Anyone wanting to hear the start of Act 4 of Ruslan and Lyudmila via the iPlayer is out of luck at the moment. The Listen Again version of today's offering starts a few minutes into the Act. The very beginning of the Act may be found at the end of the Lunchtime Concert as provided by the iPlayer. However, it seems that some may still be missing. I guess whoever is supposed to manage such matters is a devotee of P... Off Early, Tomorrow's Saturday.
Oops! I mistook the end of the extra item from the Glinka Choir for the opening of Act 4. All of which seem actually to be in tact.