Hallam (later Mattocks) was baptised in Whitechapel in 1746 by Lewis and Sarah Hallam Douglass.
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 left in the care of her aunt, Ann, and her husband John Barrington in England.

In 1762 she made her debut in the adult role of Juliet.
For most of her childhood except for a few years at school she played small parts in the productions of the Covent Garden company of actors.
When she was sixteen she joined the company and in 1765 she married her leading man George Mattocks.
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 believed to have had an affair with Robert Bensley but her marriage to George survived.

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.
She only daughter who married Nathaniel Huson in 1801.
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.
Hallam (later Mattocks) was baptised in Whitechapel in 1746 by Lewis and Sarah Hallam Douglass. 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 left in the care of her aunt, Ann, and her husband John Barrington in England.
In 1762 she made her debut in the adult role of Juliet. For most of her childhood except for a few years at school she played small parts in the productions of the Covent Garden company of actors. When she was sixteen she joined the company and in 1765 she married her leading man George Mattocks. 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 believed to have had an affair with Robert Bensley but her marriage to George survived.
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. She only daughter who married Nathaniel Huson in 1801. 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.
Isabella Mattocks