Mary married William on January 28, 1779 at Saint Leonards, Shoreditch, London, England.

National Archives (UK)
Reference: ACC/538/2nd dep/2154
Premises: two messuages in New Brentford, lease for a year. William Piper to James Knevett & George Brigganshaw, (November 23, 1778).

Reference: ACC/538/2nd dep/2155
Marriage Settlement. William Piper & Mary Knevett.
Premises: two messuages in New Brentford.
Consideration: £600 Stock in the Public Fund.
Trustees: James Knevett & George Brigganshaw, (November 24, 1778).

Reference: ACC/0891/02/01/0036
New Brentford, Manor of Colham: Copy of marriage settlement.
1. William Piper of New Brentford, butcher.
2. Mary Knevett of Old Brentford, widow.
3. Mary Knevett of Old Brentford, spinster, daughter of 2.
4. James Knevett of Isleworth, gardener and George Brigganshaw of Hoxton in Shoreditch, gent.
Total of £600 bank annuities.
Property: 2 messuages in New Brentford and 3 copyhold messuages of the Manor of Colham to 4 in trust for William Piper, Mary Knevett and their heir, (November 24, 1778).