Diaries aren't the only way to present clues to their twisted timelines. And the Doctor drops an unexpected bombshell about River's past.
River stepped back and turned off her torch pistol, she considered the symbol she'd just burned into the bottom rung of the Tardis railing.
"There!" she said with quiet satisfaction. "Now if you'll just get rid of the smoke?" she asked, waving a hand at the cloud of metal smoke around her head.
The Tardis extractor fans came on, silently, she grinned to notice, and whisked the smoke away.
The red glow of the symbol faded and as she watched the edges expanded, smoothing into perfect curves. By the time it cooled it had formed a perfect Seal of Rassilon. Looking like it had always been there as part of the architecture. The Doctor would never notice it now.
She would though, every time she came in the Tardis door. And she'd know it was after their wedding in his timeline. She grinned. She looked up at the console,