Operator London Northwestern Railway says it expects services to be busier than normal from Thursday (June 4) as Royal followers join in celebrations in the capital.
But those thinking with plans to get up early to bag a good spot for the Platinum Jubilee Pageant in London on Sunday (June 5) will be derailed.
Hundreds of thousands are expected to line streets for a 'once in a lifetime' event beginning at 2.30pm.
But the earliest Royal fans from Northampton and MK can arrive in the capital is 9.12am as engineering work means all lines will be closed between London Euston and Bletchley, forcing travellers on earlier trains to use buses.
Those with plans to head for the capital are advised to check National Rail Enquiries website before setting out.
A London Northwestern spokesman said normal weekday and weekend services will operate on Thursday, Friday, Saturday and the rest of Sunday but added: "Evening services departing London Euston will be extremely busy.
“Please plan your journey carefully and consider travelling earlier or staying over to avoid extremely busy services.
“Queueing systems will be in place during busier times to help keep you safe.”
Elsewhere on the rail network East Midlands Railway says its services from Corby, Kettering and Wellingborough will run largely as normal.
Bus operator Stagecoach will operate Saturday timetables across Northamptonshire on Thursday, Friday and Saturday and a normal Sunday service on June 5.