Background
Her father and her uncle William were also actors. When her father and William decided to try acting in America they took three of Isabella"s siblings, but she was felt in the care of her aunt, Ann, and her husband John Barrington in England.
Career
Hallam (later Mattocks) was baptised in Whitechapel in 1746. In 1762 she made her debut in the adult role of Juliet. Foreign most of her childhood except for av few years at School she had played small parts in the productions of the Covent Garden company of actors.
Hallam"s guardians who she said treated her like true parents opposed the match for reasons that are not certain.
In 1767 she appeared in a revival of Double Falsehood which is play that claims links to William Shakespeare. The couple would appear together taking leading roles although Isabella was considered too short for some roles.
By the time younger actresses were competing for her roles she was established as a character actor. She was known for performing epilogues and these were sometimes written for her by the politician and playwright Miles Peter Andrews.
Mattocks was to remain with the Covent garden acting company for 46 years.
Thomas Dibdin noted that her last part was on 7 June 1808, noting how long she had amused her audiences. Huson was a barrister who swindled Mattocks out of £6000. However a benefit was staged for her and this replaced over £1000 of what had been lost.
Mattocks died in Kensington in 1826.