I had another look through the newspapers and found a number of interesting items, including the marriage announcement for William Mumford and Ruth Ryland.
And it looks like there's another son of John Mumford, Charles Cotton Mumford, died 1862 aged 41.
Herts Guardian, Agricultural Journal, and General Advertiser
17 Nov 1855
Epitome Of News
On Sunday forenoon, as Mr Mumford, of Manor House, Shacklewell, was crossing the south end of Princess-street, by the Bank, he suddenly staggered, fell, and instantly expired. He was identified by a porter in the employ of deceased sons, lace manufacturers, in Milk-street, City. Mr Mumford, who had retired from business some years ago, and was highly esteemed in the City, had for many years been a communicant at Dr Bennett's Chapel, in falcon-square, at which place the intelligence of his sudden death were received by the office-bearers - who alone were present when the information reached them - with the deepest manifestations of sorrow. The deceased gentleman left his sons' warehouse, 1 Milk-street, on Saturday night in good health, and slept at one of his son's houses in Ludgatehill, where, on Sunday, he had appointed to dine, and to meet his family and a number of friends.
Morning Chronicle
03 Sep 1856
On the 30th ult., at the Manor-house, Shacklewell, in the county of Middlesex, Christiana Mumford, relict of the late John Mumford, late of the same place, and No 1 Milk-street, Esq., in the 65th year of her age.
London Evening Standard
05 Sep 1850
Marriages
On the 3rd inst., at St Giles', Cripplegate, James, the second son of John Mumford, of Milk-street, and the Manor House, Shacklewell, in the county of Middlesex, Esq., to Elizabeth, youngest daughter of Septimus Read, Esq., of Jewin-street.
Morning Chronicle
29 Jan 1851
Married
On the 25th inst., at Bromley St Leonard's, in the county of Middlesex, Raynham William Stewart, Esq., of the same place, to Sarah, only daughter of John Mumford, Esq., of the manor House, Shacklewell, in the county of Middlesex.
Bell's New Weekly Messenger
22 Jun 1851
Marriages
On the 17th, at Biggleswade, Mr William Mumford of Milk-street, London, to Miss Ryland, of Biggleswade, Beds.
Cambridge Independent Press
15 Feb 1873
Deaths
Mumford - At 64, Mildmay Park, Stoke Newington, Ruth, wife of Mr William Mumford, and only daughter of the late Mr John Ryland, of Biggleswade, in her 46th year.
London Evening Standard
24 Dec 1853
Marriages
On the 21st inst., at St Peter's Mancroft, Norwich, Henry, fourth son of J Mumford, of the Manor House, Shacklewell, Esq., to Mary Emily, second daughter of Mr S Sendall, of the former city.
Reading Mercury
13 Sep 1862
Deaths
On the 29th ult., at Alton, Hants, Charles Cotten, fourth son of the late Mr Jno. Mumford, of No 1 Milk-street, City, and the Manor House, Shacklewell, London.
Bell's Life in London and Sporting Chronicle
19 Apr 1840
To Drapers, Milliners, &c.
To be disposed of immediately, in consequences of the proprietor declining business, an old established business in the above line, in a market town, surrounded by the most respectable neighbourhood. The premises are well situated for trade, and in good repair. Stocks and fixtures about £700 or £800. For particulars apply to Mr Mumford, No 1, Milk-street, Cheapside, London.