Transport for London achieved a huge breakthrough in the Tube dispute when it managed to run services on the Northern line.Trains began running on the full length of the line, which extends from High Barnet and Edgware in north London to Morden in the south, from 8am on Tuesday.With the Elizabeth line unaffected by the Tube dispute, this meant that TfL succeeded in opening up key east-west and north-south routes through central London.TfL will aim to open the Northern line again on Thursday – when, like on Tuesday, Tube drivers will not be part of the walkout.Sections of other lines could open on Wednesday, depending on staff turnout, but TfL will continue to prioritise keeping the Elizabeth line open after a record one million journeys were made on the “Lizzie line” on Monday.