Thousands of people are expected to line the streets of Wells, as they pay their respects to the last British veteran of the first world war trenches who died at the age of 111 at his care home in Wells.
The bells of Wells Cathedral will toll 111 times to mark every year of Harry's life at 1100. It is expected this will take around 50 minutes.
At approximately 1130, Harry's coffin will begin its journey from his care home Fletcher House to the cathedral.
The hearse will leave Fletcher House and will travel along Glastonbury Road and Priory Road.
The coffin will be flanked by six private soldiers of the Rifles Regiment, the successor to Harry's Regiment, the Duke of Cornwall's Light Infantry.
In this way, it is hoped to symbolise Harry's desire for reconciliation and his view that "irrespective of the uniforms we wore, we were all victims".
It will pass up Broad Street and onto the High Street, then left on Sadler Street, turning right onto the Cathedral Green, through West Gate.
Members of the public are encouraged to pay their respects to Harry by lining the route of the cortege as it travels through the centre of Wells to the cathedral. Silence is requested.
Road closures will be put in place - with some taking place from 1800 on Wednesday and 1000 on Thursday.
All of the tickets for church service have now been allocated, but organisers plan to relay the service onto screens on Cathedral Green for people unable to get tickets.
The service will begin at midday and will be led by the Dean of Wells, The Very Reverend John Clarke and Bishop of Taunton and The Rt Revd Peter Maurice and there will be reading from representatives of the Belgian, French and German governments.
The Royal family will be represented by the Duchess of Cornwall and Duchess of Gloucester.
The service will end outside the cathedral at Great West Gate where the last post will be sounded and Harry's coffin will be taken for a private burial.
We'll be broadcasting the service live on our website, bbc.co.uk/somerset