Closing of the Rift

In 1869, the Cardiff Space-Time Rift was closed by Gwyneth. (TV: The Unquiet Dead)

Aftermath and legacy
Rose Tyler noted the Gelth among the things she had seen when she was sceptical that the newly regenerated Tenth Doctor was the man she knew. (TV: Born Again)

While attempting to bluff the Sycorax into leaving Earth alone, Rose tried to invoke the authority of the "Gelth Confederacy", among other species she had encountered on her travels. (TV: The Christmas Invasion)

Rose suggested that the Gelth may have been responsible for the ghost shifts. The Tenth Doctor discredited this, observing that these ghosts were appearing all over Earth; they were ultimately found to be the Cybus Cybermen, who launched an invasion from Pete's World. (TV: Army of Ghosts)

Upon coming into contact with Gwen Cooper of Torchwood Cardiff, the Tenth Doctor had her confirm that she came from an old Cardiff family. He noted to Rose that she resembled Gwyneth as a result of spatial genetic multiplicity. (TV: Journey's End)

Alternate timelines
In world that never was, (TV: The Wedding of River Song) Charles Dickens blocked @TheGelth on Prof. T. Witter's Instant Messaging Service, telling them that he wasn't "falling for that one again". (PROSE: Just a Minute...)