In St Paul's Cathedral, St Paul would be the obvious (but not comfortable) choice. I like the way Paul used the word 'saints' to mean something very different from unusually special people who end up with a halo in a stained glass window. Whenever St Paul wrote to a church he wrote "to the saints...", all the Christians in that place. His letter to the Romans begins, "To all God's beloved in Rome, who are called to be saints...". It's a calling most of we Christians don't live up to at all well. We "called-to-be-saints" are saints-in-the-making, ordinary fallible people who make mistakes. We're not perfected saints in heaven. Well you knew that didn't you?
Do you know the story of the boy whose teacher asked him, "what is a saint?" He'd recently been taken to visit a cathedral with magnificent stained-glass windows with pictures of saints. He thought for a moment, then said, "a saint is someone the light shines through".
How well the light shines through a window depends on the properties of the glass, how well it's crafted to let the light pass through and how clean it is. But, as long as the light is bright enough some rays get through even the dullest rough glass. However much daylight reaches the inside of a church through its windows, it's always brighter if you step outside.
St Francis of Assisi is said to have taught his monks that even should they be entranced by a vision of heaven, if a tramp knocked on the door and asked for water then turning to help the tramp would be the real heavenly vision. Turning away from the tramp would be to turn away from God's face. Peter Kreeft points out that the real saint is the one who sees who the tramp is: Jesus.