Short answers, pulled from the story.
Thomas Attwood studied under Mozart in Vienna. The Prince of Wales funded Attwood's time abroad beginning in 1783, and after two years in Naples, Attwood moved to Vienna where he became a favourite pupil of Mozart.
Attwood played his own composition, the Grand Dirge, on the organ at the funeral of Lord Nelson in January 1806. It was the only piece specially written for that occasion.
Attwood composed a setting of the anthem I Was Glad for the coronation of George IV, and it was reused at the coronations of King William IV and Queen Victoria. He also wrote O Lord, Grant the King a Long Life for William IV's coronation.
Attwood and Mendelssohn formed a close friendship after Attwood heard him play in London in 1829. When Mendelssohn injured his leg falling from a carriage, Attwood invited him to recover at his home in Norwood. Mendelssohn dedicated his Three Preludes and Fugues for the Organ, Op. 37, to Attwood, and composed The Evening Bell inspired by the gate bell at Attwood's house.
Thomas Attwood is buried in the crypt of St Paul's Cathedral, under the organ. His funeral took place at St Paul's on the 31st of March 1838, a week after his death at his house at 75 Cheyne Walk, Chelsea.
Attwood taught John Goss, Cipriani Potter, the child prodigy Elizabeth Jonas, and his godson Thomas Attwood Walmisley. Through his friendship with Mendelssohn, he also encouraged the young William Sterndale Bennett.