"In 1889 the Administrative County of London was formed from the City of London, and parts of Middlesex, Kent and Surrey and was divided into boroughs. In 1963 this County was replaced by Greater London which also took in the rest of Middlesex and parts of Essex and Herts as well as some county boroughs. New London boroughs were then formed." [T.V.H. FitzHugh, The Dictionary of Genealogy, 1994.]
London Metropolitan Archives, 40 Northampton Road, London EC1R 0HB - holds the archives of the Greater London Council, the London and Middlesex County Councils and their predecessors, and most parish registers.
Pevsner's "The Buildings of England" published by Penguin Books in the 1950s to 1970s, is a comprehensive survey of current notable buildings which also includes history of buildings since demolished. It is being brought up to date, and is now published by Yale University Press. London is being covered by six hardback volumes.
Deaneries in 1903 with links to lists of parishes of the part of the historic county of Middlesex which was in the County of London in 1903. These also link to lists of churches indicating the formation dates of parishes, and location of records - currently for the inner part of Middlesex.
The COLLAGE database (Corporation of London Libraries and Guildhall Art Gallery image database) has very many images related to the churches of Middlesex. Simply search on the church name or the place-name plus 'church' to find relevant images.
London churches and olde celebrities by John Blythe Smart (Blythe Smart Publications, Kingsbridge, Devon, 2012) lists and describes, with many architectural illustrations, almost all the churches and chapels in inner London (the former London County Council area). Volume 1 covers the City and Volume II the 'environs'.
Description from Barclay's Complete and Universal English Dictionary, 1842.)"A county of England, bounded by Hertfordshire, Essex, Surrey, Kent, and Buckinghamshire. It is one of the least counties in England, being only about 22 miles in length, and 14 in breadth. It contains 7 market towns, and about 98 parishes, without including those in London and Westminster. The air is healthy; but the soil in general being a lean gravel, it is naturally a district of little fertility, though by means of the vicinity to the metropolis, many parts of it are converted into rich beds of manure, clothed with almost perpetual verdure. Besides the Thames, the Lea, and the Coln, Middlesex is watered by several small streams, one of which, called the New River, is artificially brought from Amwell, in Hertfordshire, for the purpose of supplying London with water. Indeed, the whole county may be considered as a demesne to the metropolis, the land being laid out in gardens, pastures, and enclosures of all sorts, for its convenience and support. London is its chief place, and county town. Population, 1,576,636."
Middlesex Protestation Oath Rolls 1641-2. CD published by Mike Gallafent, email <firstname.lastname@example.org>.
'Strangers, Foreigners & Aliens' CD also published by Mike Gallafent, email <email@example.com> is in two parts; the first is of aliens (including Scots!) & their family details, living in London in 1567.
Victoria County History of Middlesex - this has a substantial amount of information on-line including draft text of parish histories for Westminster, and complete text of forthcoming volume of parish history for Chelsea.
Middlesex Deeds Registry By an Act of Parliament of 1708 a registry was established for the registration of all deeds,conveyances, wills, encumbrances, etc, affecting freehold land and land held by a lease forover 21 years within the ancient county of Middlesex. The City of London was not included. The records are at the London Metropolitan Archives.
Mike Durtnall's Historical Manuscripts Pages (http://www.durtnall.org.uk/DEEDSIndex.html) included information about many descriptions of historical documents taken mainly from online auction catalogues, including nearly 2000 referring to London or Middlesex. [As of February 2008 this site has only been intermittently available. You may find an old version on the Wayback Machine.]
Family Deeds provide abstracts of old deeds and documents sold on the open market. They have pages for deeds referring to places in London and Middlesex.
The former County Asylums website had information about the local authority funded mental hospitals in London (both the City of London and the 1889-1963 London County Council) and in Middlesex.
Simon Forman, the notorious London astrologer, recorded 10,000 consultations between 1596 and 1603. Most of these are medical. Forman's casebooks can now be searched by name (of any party involved), date, sex, age, topic of consultation and many other criteria. The edition includes images of all the manuscript pages of Forman's first volume, and more will follow. They are available from the Casebooks Project at the Department of History and Philosophy of Science of the University of Cambridge
Land Tax was levied 1692-1932. Ancestry have indexed the records held at LMA, covering the City of London, Middlesex (including most Westminster parishes), and some parishes in Kent and Surrey. Full information is given in a leaflet from LMA.
Visitations by the Heralds were designed to record the pedigree of armorial families and to confirm their right to bear arms. There is a good guide to them on Chris Phillips' Medieval English Genealogy site. The vistations of 1572, 1634 and 1663 together withother pedigrees are published in the Harleian Society volume 65: Armytage GJ (ed) (1913) Middlesex pedigrees as collected by Richard Mundy in Harleian Manuscript No. 1551. Available on CD from Archive CD Books.