man Thomas HOWARD‏‎    , son of William HOWARD and Elizabeth‏.
Born ‎1731 Caddington, Bedfordshire, England, baptised ‎19 Dec 1731 Caddington, Bedfordshire
Possibly Baptised 17th June 1753 son of Joseph and Susana Howard of St Stephens (Unlikely though)
More likely to be:
Baptised 19 Dec 1731 son of William Howard and Elizabeth of Caddington, Beds.
Familysearch record:
First name(s) Thomas
Last name Howard
Gender Male
Birth year -
Birth place -
Baptism year 1731
Baptism date 19 Dec 1731
Place Caddington
County Bedfordshire
Country England
Father's first name(s) William
Father's last name Howard
Mother's first name(s) Elizabeth
Mother's last name -
Record set England Births & Baptisms 1538-1975
Category Birth, Marriage, Death & Parish Records
Record collection Births & baptisms
Collections from Great Britain

Married ‎16 Jan 1753 Kimpton, Hertford, England Marriage to Sarah is the only one in the Hertfordshire area within 20 years of son Joseph's birth so it is assumed the details on the Wedding Register correspond to the two individuals.

Update 11 Apr 2016
Another Thos. Howard and Sarah found in Index of Clandestine Marriages

http://search.ancestry.co.uk/cgi-bin/sse.dll?gss=angs-c&new=1&rank=1&gsfn=thomas&gsfn_x=0&gsln=howard&gsln_x=0&msbdy=1731&msgdy=1750&msgdy_x=1&msgdp=10&mssng=sarah&cpxt=1&cp=4&MSAV=1&uidh=a74&pcat=34&h=84975&recoff=6+7+26&db=FleetMarriageBap&indiv=1&ml_rpos=25

Name: Thos Howard
Gender: Male
Event Type: Marriage
Marriage Date: 5 Jun 1748
Marriage Place: London, England
Residence: Redburn, Hertfordshe
Spouse: Sarah Young
Piece Description:
Officiating Ministers: Wyatt. Wyatt's register. (1746 Mar - 1749 Oct, 1746 Jun - 1750 Feb)

and

Piece Description: Fleet Notebooks (Wyatt), 1748 Mar - Jun

Notes about this register:
About London, England, Clandestine Marriage and Baptism Registers, 1667-1754Rules of Marriages

Ecclesiastic laws governing marriage have changed during England’s history, and during this period (1667–1754), marriage within the church came with certain restrictions. Banns required a couple to post an announcement of the intended union for three weeks prior to the marriage. Banns could be waived by obtaining a license, but church officials could also dictate where and when a couple could marry. Residency requirements, although at times loose, had to be met, and there were certain times during the ecclesiastic calendar when marriages were not to be performed. There were also age restrictions: parental consent was required if either party was under the age of 21.Most couples were married at the family church, but a significant portion of the population, for various reasons, chose to skirt these regulations and get married outside the church. Here, requirements were much looser. Grooms could be as young as 14, and brides 12. The bride and groom needed only to give their consent to the union for it to be recognized. Clergy and witnesses were not necessary, though they were often present to provide proof that the marriage had taken place. These marriages are commonly referred to as “irregular” or “clandestine.

Who Performed Clandestine Marriages?
The demand for clandestine marriages was met by institutions that considered themselves exempt from church canon and in some cases, like that of May Fair chapel, by a cleric who simply flouted the regulations.Prisons like the Fleet and the King’s Bench Prison became popular destinations for couples interested in quick, no-questions-asked nuptials because of the number of clerics imprisoned for debt who had nothing to lose and welcomed the income. Many of them lived in the “Rules” or “Liberties,” which were areas around the prison where prisoners could pay for the privilege of living outside the gates.In an effort to crack down on clandestine marriages, legislation in 1711 attempted to coerce prison keepers to require banns or licenses before performing marriages. That legislation only succeeded in pushing more marriages outside the prison walls into the Rules, or in the case of King’s Bench Prison into the area known as “the Mint,” until the passage of Hardwicke’s Act of 1753, which went into effect March 24, 1754, and required formal ceremonies, thus shutting down the marriage centers.

What You May Find in the Records
The contents and format of the registers may vary slightly, but they will typically include the following details:
full names of the couple (in some cases a maiden name may be absent)
marital status
residences (generally parishes)
occupation of the groom
minister's name or initials
This collection also contains about 2,800 records of clandestine baptisms.
to:

woman Sarah "Sarah Sebrooke" Seabrooke‏‎ Name on Marriage register is Sebrooke    , daughter of John Seabrook and Mary Beckford‏.
Born ‎1722 Saint Stephens, Saint Albans, Hertfordshire, England, Great Britain, baptised ‎21 Mar 1722 Saint Stephens, Saint Albans, Hertfordshire

Child:

1.
man Joseph HOWARD‏    
Born ‎1770 North Mimms, baptised ‎18 Mar 1770 North Mimms, died ‎1850 North Mimms, Hertfordshire, England, United Kingdom‎, 79 or 80 years, death cause: Not on 1851 Census, buried ‎23 Jun 1850 North Mimms, Hertfordshire, England, United Kingdom Registered by J G Faithful, Vicar. Occupation: ‎1841 Aldenham, Hertfordshire, England; Labourer