Who's that man walking just behind the Queen?

Feel rather sorry for the Duke of Edinburgh - his (real) 95th birthday was completely overshadowed by the celebrations for the (official) 90th birthday of the Queen.  Her real birthday was of course several weeks ago.  The Duke has spent his married life taking second place to the Queen and it would have been nice if just for once he had been allowed to take centre stage, if only for the day.