Sir Sadiq Khan has urged the RMT union not to press ahead with a Tube strike that could cause three weeks of chaos for passengers. It came as The Standard learned that the impact of the strike could be much worse than initially expected for commuters and businesses. There could be “limited or no service” on the London Underground from Tuesday morning until Friday afternoon on each of the three weeks earmarked for the walkouts. On Wednesday, the London mayor urged union leaders to return to the negotiating table and resolve their differences with Transport for London “amicably”. The RMT, which Sir Sadiq described as a “good trade union”, has announced six 24-hour walkouts starting on March 24 and continuing in April and May. But because each of the strikes starts at midday and finishes at midday the following day, before resuming a day later, it is feared this will cause significant disruption over four consecutive days –Tuesday to Friday – in each of the weeks earmarked for action. Soon after the strikes were announced …