Talks with other devolved leaders were held at Downing Street.
Queen's Record Reign Celebrated
The Army will commemorate the Queen becoming the longest reigning monarch in British history today with a "dignified restraint''.
In recognition that the calculations for the historic day rest on the moment the Queen's father and great-great-grandmother Queen Victoria died, the Army's tribute will be more reflective.
An Army spokeswoman said: "The Army's tribute to their Commander in Chief has a dignified restraint.
"A Drumhead Service will be held in Bury St Edmunds with 6 Army Air Corps, and in London, the Household Division, which enjoys a uniquely close relationship with the sovereign, has arranged for the Band of the Coldstream Guards to perform a bespoke piece of music which will be released on the day.''
Forty musicians from the band will perform the quintessentially British piece Vivat Regina (Long Live The Queen), the first of Four Historical Portraits by composer and band leader Laurie Johnson who has scored a number of films including Dr Strangelove.
Director of Music Major Simon Haw said: "It is a huge privilege to be marking this historic occasion on behalf of the Household Division. The piece of music we have chosen: Long Live The Queen is something we all long for.''
At around 5.30pm the Queen will surpass Victoria's reign of 23,226 days, 16 hours and 30 minutes.
Victoria was 18 when she acceded to the throne, the Queen was 25. The length of reign has been calculated by experts at the Royal Household to the nearest point of accuracy, taking into account leap days in both reigns.
Stefano Brizzi is accused of murdering the Scottish police officer.
It happened in the Govanhill area at lunchtime.
It's being treated as attempted murder.
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