Visitor Visa - Change of travel Date

[labrepro]

Hi All,

My parents got their visitor visa stamped but due to personal reasons, they could not travel on the dates we specified. Current visa runs out in end of November. New plan is they want to travel in mid November and spend Christmas and new year in the UK.

Question - Do they need to file a new visa application like they did first time? Or is their a procedure using which they could simply get the visa expiry date changed?

[CR001]

I suspect that they will need to apply for a new visa with all the same evidence.