London's farm (i.e. the estimated total of the various revenues due the king) was £300 at the time of Domesday, but by 1130 had risen to just over £525, a sum whose collection may have required extortionate measures to achieve, particularly in the context of a serious fire in the city which had just occurred and must have reduced the citizens' financial means. The collectors of the revenues that went towards the farm failed substantially to meet the required sum in 1130. These revenues were collected by sheriffs over whose appointment the citizens had no control, until that same year when evidence suggests the Londoners had persuaded the king to turn over responsibility for the farm, with concomitant election of the sheriff, to them temporarily.

Such were the circumstances believed to have produced, within the next year or so (a recent theory on the date favours 1133, in which year a major fire in the city further damaged its ability to pay the farm [C. Warren Hollister "London’s first charter of liberties : is it genuine?" Journal of Medieval History. vol.6 (1980)]), the charter attributed to Henry I; this restored the farm to its traditional amount, confirmed the grant the farm (of the small county containing London) to the citizens, and gave them the right to elect the collectors as well as a measure of judicial independence in the form of electing a justiciar, a local office which had proliferated during the reign of William Rufus; the Londoners associated this office, rightly or wrongly, with the earlier institution of lawmen, which also involved expert knowledge of, and the ability to interpret, local laws. Henry, who had seized the throne over the claims of an older brother (and has even been suspected of assassinating of his predecessor) and by 1130 was looking for support for the unprecedented succession of a daughter to the throne, was desirous of approval from any quarter. This, together perhaps with a wish to avoid the spectre of the revolutionary commune which had recently plagued Flanders, may have been sufficient motivation for Henry to satisfy some of the ambitions of his kingdom's most important town.

Overall, historians accept that the customs identified in the charter are quite credible for the date represented by the grant. Yet the generous terms of the charter – from a king not renowned for giving something for nothing, and not duplicated for any other town – regarding the substantial reduction of the farm (seemingly in perpetuity), grant of the shrievalty, and the apparently extensive jurisdiction of the justiciar, have given rise to concerns that the charter might be a forgery, or have undergone later interpolations, or even actually be a grant by Stephen later changed to attribute it to the more authoritative Henry I. Careful study of the document has raised the level of doubt by identifying a number of small issues that look suspicious; none of them insuperable, however, and it is probable enough that the Londoners paid Henry a hefty lump sum to have the charter.

No original of the charter has survived for us. The text is known through a large number of copies none of which appears to have avoided corruption. The earliest version – in a rambling collection of twelfth-century laws, national and local, that was compiled during the conflict between King John and his barons, and useful to the latter party in forcing the king to make concessions – is one of the more corrupt. There is evidence that by this time, or shortly afterwards, the charter had already gone missing. This loss need not itself be a major cause of suspicion, given the informality of archival practices in a time when there was no structured urban bureaucracy, given the disruptions of the Anarchy (from which the capital did not emerge unscathed), and given the fact that not a few charters of Henry II refer back to grants of liberties made by Henry I for which no original documentation has survived.

In defence of the authenticity of the charter, the reasons why Henry might have been prepared to conciliate London are indicated above. It may also be noted that many towns had their farms reduced in the decades following Domesday (although London's was not the only one to increase), so a reduction of London's – in the face of possibly strong arguments as to its unreasonably high level – is not incredible. Despite Henry's attempt to garner support for his chosen successor, it was to Stephen that London quickly gave its support in the contest for the throne. Yet neither Stephen nor Matilda appear to have paid any attention to the terms of Henry's charter; both gave the shrievalty of Middlesex to Geoffrey de Mandeville, in an attempt to win his support. In the same year (1141) London resorted to an attempt to create a commune that asserted its rights; this might have created a situation in which Stephen could have issued a charter later attributed to Henry.

Henry II's charter to London of ca.1155, whose authenticity is not questioned, was basically a confirmation of the Henry I charter. A comparison of the two strongly suggests the latter, whether genuine or forgery, was written first. Henry II, however, was not inclined to generosity, and may have had a grudge against London for its actions against his mother. While accepting the authenticity of his grandfather's grants, he reined back on their terms, omitting control of the farm (which, when evidence reappears, shows the farm at a £500+ level) and grant of the elected officers. Among lesser differences is the substitution of exemption from brudtoll, childwite, ieresgive and scot-ale (see Northampton's charter), in place of Danegeld and scot and lot – a credible update, Danegeld (12d per hide per year) having become irrelevant as a tribute to occupying forces.

On the whole, historians are prepared to give Henry I's charter the benefit of the doubt, although some continue to think it a later forgery. The most contentious issue is the level of the farm, which may represent revisionism. It was left for Henry II's sons – the one in need of money for crusading, the other pressured by a new outbreak of the assertive commune in London and baronial opposition throughout the realm – to satisfy the full ambitions reflected in a document which almost certainly was drafted in the second quarter of the twelfth century.