Christians from all over the country have gathered in Buckinghamshire...
Queen's chaplain: Queen knows that God knows her heart very thoroughly
The Chaplain to the Queen, Canon Ann Easter, has told Premier that the: "I reckon that the Queen knows God that knows her heart very thoroughly."
Wednesday marks Queen Elizabeth as Britain's longest reigning monarch and the occasion was marked with a procession down the River Thames, led by Queen's rowbarge Gloriana.
London's BT Tower will also be displayed the message "Long May She Reign".
The Queen thanked everyone at home and overseas for their "touching messages of great kindness" on the day.
The record for longest reigning royal was previously held by her great-great-grandmother, Queen Victoria - of more than 63 years.
The exact time that the Queen passes Victoria's milestone is not known as there is no precise time for the death of her father, George VI - who died in the early hours of February 6th 1952.
The Prime Minister, David Cameron, will be leading tributes to the Queen, describing her as a rock of stability in a world of constant change.
Her Majesty Queen Elizabeth has served for 63 years and 216 days to date..
She has been visiting Edinburgh and meet Scotland's First Minister Nicola Sturgeon.
The train traveled on was drawn by the steam locomotive Union of South Africa.
To celebrate a new official picture has been released taken by celebrity photographer Mary McCartney - showing the Queen at her desk in Buckingham Palace.
Churches will ring their bells and special prayers, approved by the Palace, will be read at services across the country.
Canon Ann Easter, the Queen's Chaplain told Premier that: "My mum and her Majesty were born in the same year and I know how much her faith meant to my mum - in a very simple and straight foward way - and my feeling is probably with the Queen it's just the same.
"Her trust is faithful, there's that sureness that whatever happens - all the different things in life she's seen, and she's also experienced sadness herself - but whatever happens that faith, she might not be happy but she'll know that joy of being loved by God and cherised and valued for herself."
Well wishers are gathering in Edinburgh waiting for the Queen's arrival.
Sir John Major, one of the 12 prime ministers of Elizabeth II's reign to date, described Queen Elizabeth as an "absolute constant" in British life.
Sir John told BBC Radio 4's Today Programme: "Throughout the last 60 or so years, the Queen has been an absolute constant.
"Whilst prime ministers have come and gone, celebrities have come and gone, life has changed, she and the monarchy have been an absolute constant in their lives and I think that is very reassuring."
Listen to Premier's John Pantry speak to Canon Ann Easter here:
Premier's Des Busteed was live outside Buckingham Palace for the News Hour. You can hear his conversation with two well-wishers, Ann and Lynn, here: