Former Boris Johnson aide Dominic Cummings is set to give explosive evidence at the COVID public inquiry this week. Once a close ally of Mr Johnson, Cummings is now his sworn enemy and is expected to reveal damaging information about the former prime minister. He leads a list of former Downing Street insiders who will be questioned during the inquiry. Cummings' testimony is scheduled for Halloween, prompting speculation about the haunting questions he will face regarding “partygate” and lockdowns.

Among the other witnesses are Martin Reynolds, a former private secretary nicknamed "party Marty" for his notorious email encouraging Downing Street staff to bring their own booze. Reynolds will be the first witness this week, followed by Lee Cain, the former director of communications and self-proclaimed expert in crisis management.

Cummings will take center stage on Tuesday, with his testimony anticipated to be as sensational as his previous appearance before a committee of MPs two years ago. During that appearance, he accused Johnson of not initially taking COVID seriously and changing his mind frequently, as well as criticizing former Health Secretary Matt Hancock for dishonesty. Cummings also admitted that his trip to Barnard Castle during lockdown, which he claimed was to test his eyesight, was a "terrible mistake."

This week, Cummings is expected to launch further attacks on Johnson, as well as Johnson's wife Carrie, Hancock, and cabinet secretary Simon Case. Notably, Case will be absent from the evidence sessions due to sick leave.

The inquiry is also expected to unveil embarrassing WhatsApp messages exchanged between key Downing Street figures, including Cummings and Johnson. Some damaging messages have already been released, such as Johnson dismissing long COVID as "b*******" and Case referring to Carrie as "the real person in charge." Additionally, former Chancellor George Osborne has claimed that "disgusting and misogynistic" WhatsApp messages between Johnson and Cummings will be made public this week.

Both Johnson and current Chancellor Rishi Sunak are expected to attend the inquiry in December. Sky News deputy political editor Sam Coates emphasized the significance of this week's evidence, particularly since some individuals involved in the inquiry are still part of the government.

Coates anticipates that Cummings' testimony will include a significant amount of score-settling and attacks on Johnson, Hancock, and various aspects of the civil service. He characterizes No 10 as dysfunctional, with Johnson and his closest advisers seemingly working against each other.

Other witnesses giving evidence this week include Imran Shafi, former private secretary to the prime minister; Helen MacNamara, former deputy cabinet secretary; Lord Stevens of Birmingham (previously Sir Simon Stevens, boss of NHS England); Sir Christopher Wormald, permanent secretary of the Department of Health and Social Care; and Professor Yvonne Doyle, former director for health protection at Public Health England.

The hearings are expected to shed light on the workings of Downing Street during a critical time for the country and are likely to be used by the Labour Party to their advantage. Banter between Case and Cain, described as "laddish, football-style," has already raised concerns, and further examples of such behavior are expected this week, potentially damaging Case's position.

Furthermore, it has been revealed that Cummings has chosen not to use a lawyer while preparing for his testimony, leaving him vulnerable to challenges from other witnesses.