Short answers, pulled from the story.
Johann Christian Bach (the 5th of September 1735 - the 1st of January 1782) was a German composer of the Classical era and the youngest son of Johann Sebastian Bach. He is significant for developing the sinfonia concertante form, teaching the young Wolfgang Amadeus Mozart, and winning the landmark copyright case Bach v Longman in 1777, which established that English copyright law applied to musical scores.
Bach met Mozart in 1764, when Mozart was eight years old, and spent five months teaching him in composition. Scholars Teodor de Wyzewa and Georges de Saint-Foix described Bach as "The only true teacher of Mozart." Mozart arranged three sonatas from Bach's Op. 5 into keyboard concertos, and his Piano Concerto No. 12 references the overture of Bach's opera La calamita de cuori.
Johann Christian Bach became known as "The English Bach" after settling in London in 1762, where he premiered operas at the King's Theatre and became music master to Queen Charlotte. He spent the rest of his career there, performing at the Hanover Square Rooms and co-organizing the influential Bach-Abel concert series.
Bach v Longman was a landmark 1777 legal case that established in English law that copyright protection applied to musical scores. Johann Christian Bach had been pressing for recognition of his rights as a composer since arriving in London in 1762, when he was granted an exclusive right to publish his music for fourteen years.
The Bach-Abel concerts were a public subscription concert series organized by Johann Christian Bach and German viola da gamba virtuoso Carl Friedrich Abel. They opened classical music to the middle class by offering prepaid seasonal subscriptions, in contrast to the private aristocratic settings where live classical music had previously been confined. The concerts also featured newer composers including Haydn.
Johann Christian Bach died on New Year's Day 1782, deeply in debt in part because his steward had embezzled his money. Queen Charlotte, whom he had served as music master, covered the expenses of his estate and provided a life pension for his widow, soprano Cecilia Grassi. He was buried in the graveyard of St. Pancras Old Church in London.