The highest ranking civil servant position is the Principal Private Secretary to the Prime Minister; the most senior special adviser post is the Downing Street chief of staff.

[7] Since 2005, Number 10's Direct Communication Unit has not used its staff's real names on signed correspondence to MPs and members of the public; this is for security reasons.

In 1806, the role of Private Secretary to the Prime minister was placed on an official footing, when his salary began to be paid from public funds.

[10] By this time the office had begun to be more civil service dominated: between 1922 and 1928, despite several changes of prime minister and a change of government from Conservative to Labour, three of the four Private Secretaries had remained in post; since when the post of Principal Private Secretary has almost invariably been occupied by a career civil servant.

Alastair Campbell's influence, as press secretary under Tony Blair, was even greater, and in 2000 he was given a more senior role as Downing Street Director of Communications, with the authority to issue directives to civil servants.

By the 1930s, the Private Office had largely become the preserve of civil servants, leaving no obvious place in the structure for the Prime Minister's political advisers.

[9] By the time John Major took over as prime minister, the Political Office was a loose grouping which included: The Policy Unit was also established by Harold Wilson, ten years later (in 1974).

The first prime minister to appoint a chief of staff was Margaret Thatcher in 1979; David Wolfson was one of her closes aides, and when he resigned in 1985 he was not replaced.

After Cummings's departure, Lister served as acting chief of staff before being replaced by Dan Rosenfield, who officially assumed the role in January 2021.

She said this needed to be addressed as a priority, and Boris Johnson agreed to the Office of the Prime Minister becoming a Government department.

[22] Several changes in staffing took place early in February 2022 and the role of Downing Street Permanent Secretary was set to be revived, with Samantha Jones holding the position on an interim basis;[23] but the plans were not carried forward after Johnson's resignation as prime minister.