Major disruption is expected after a main railway line collapsed in a “huge” landslip which left one track hanging in mid-air.
The damage has left only two of the four-track railway passable, with both these tracks designed for London-bound trains only.
South Western Railway is advising customers to check before they travel and to plan alternative transport for journeys to or from the south or west of Basingstoke to London on Monday.
Network Rail Wessex route director Mark Killick said: “This is a huge landslip and will have a massive effect on customers. The main line to Basingstoke is the spine of our railway and there will be knock-on impacts across the route.
“I can only apologise for the scale of the disruption and please ask that customers check before they travel this week, not just on the affected section, but all the way up the line to London Waterloo, where many of the trains that would use this section of railway start and finish their journeys.
“We’re still assessing the damage and it’s difficult to put a detailed timescale in place, but we know it’s going to be at least a week.
“We will need to stabilise the embankment, essentially stopping it moving, and then rebuild the railway where it has slid away.
“We’ll keep everyone informed of our progress and I can only say thank you to everyone for their patience and apologise again for the disruption. Please look out for further updates from South Western Railway on the revised timetable, once this has been able to be confirmed.”
A Network Rail spokesman explained that the embankment was made of a mixture of London clay and other local soils which had become saturated after days of heavy rain.
He said: “The slip happened when the soil gave way along a 44-metre section of 10m-high embankment, sliding out from underneath the tracks, in what engineers call a ‘rotational failure’.
“Network Rail and its suppliers are working on designs for the work needed to repair the railway, which will give a clearer idea of timescales.
“In addition, a train plan to provide journey options for customers on the route will be published as soon as possible.