The new overground extension to Clapham Junction was suspended for almost an hour yesterday.
Signalling failures at Peckham caused trains on the new route to be suspended between 1.05pm and 2pm, much to the frustration of commuters.
Travellers from Wandsworth Road, Clapham High Street, Denmark Hill, Peckham Rye and Queens Road Peckham were all affected.
Howard Smith, chief operating officer at TfL, said: "A signal failure near Peckham caused services to be suspended between 1.05pm and 2pm yesterday.
"This failure occurred on existing track not on the new infrastructure brought into use last Sunday."
The new route was launched on Sunday, with the Mayor of London joining passengers on Monday.
It is the first orbital railway to open in the capital in 128 years, with Boris Johnson dubbing it the 'M25 of rails'.