Unlike government bills, PMBs are not timetabled (that is, they are not subject to a programme motion).

As a consequence, only the first PMB on the Order Paper each Friday is certain to be debated. If the debate ends before 2.30pm then the second bill and possibly subsequent bills may be reached in the remaining sitting time. But after 2.30pm only those PMBs that are unopposed make progress.

At the start of a PMB Friday sitting an MP may move the motion "that the House do sit in private". The quorum is 40, including the Speaker or Deputy Speaker and tellers. If fewer than 40 MPs vote, then the bill will be deferred to the next PMB sitting day. In practice, this means the bill is unlikely to progress any further. But if 40 MPs support the motion then the debate on the first PMB listed on the Order Paper commences.

The reason for moving the motion at the start of the sitting is to prevent another MP (who may be opposed to the first PMB or to another bill listed further down the Order Paper) from moving the motion later in the sitting when there may be fewer than 40 MPs in the Chamber. If another MP were successful in forcing a division involving fewer than 40 MPs then it would stop the bill from being debated further. This is a procedural hazard on Fridays when most MPs are in their constituencies rather than at Westminster.

The lack of a programme motion and time limits on speeches mean a handful of MPs can time-waste and filibuster a PMB. Just one or two MPs can talk out a bill and ensure that debate is not reached on bills lower down the Order Paper.

The Speaker has the power under Standing Order No. 47 to place time limits on speeches. However, it has long been common practice that during PMB proceedings the Chair does not impose any limit.

If debate is still ongoing at 2.30pm, and there has been no interruption, then the debate ceases and the bill is scheduled to resume at a later Friday sitting.

The rules militate against proper debate of PMBs because any interventions by MPs in support of a bill help to run down the clock. Every minute an intervention takes up is another minute the bill's opponents do not have to fill with their own filibustering tactics.

Occasionally, a popular bill that has been talked out by just one MP has been subsequently adopted as a government bill to get it on to the statute book as soon as possible (for example, two bills talked out by Christopher Chope MP: the Upskirting Bill (15 June 2018) and the Children Act 1989 (Amendment) (Female Genital Mutilation) Bill (8 February 2019)).

Forcing a division (on either the quorum or a closure motion) can also be used as a time-wasting tactic. The Speaker will try to adjudicate a vote on the basis of the shouts of "Ayes" and "Noes" when the question is put, but if the shouting is vociferous then a division will be called and more time will be eaten up.

Divisions in which only a few dozen MPs may be participating can take as much as 15-20 minutes each, as opponents of the PMB try to delay matters as long as possible. It is not uncommon for the Speaker to have to call on the Serjeant at Arms to investigate the delay.

The only way to bring debate to an end and avoid the Second Reading of a PMB being rescheduled (often months later) is through a closure motion. If opponents of the bill are speaking as the moment of interruption at 2.30pm nears then supporters of the bill must move "that the Question be now put".

The timing of a closure motion is crucial as the Speaker will not allow such a motion to be put at Second Reading (or on an amendment at Report stage) if he deems that there has been insufficient debate. However, closure motions can usually be requested successfully within the final hour of the sitting.

To win a closure motion and successfully bring debate to a close, at least 100 MPs must vote in favour of the motion. On a Friday, when many MPs are not at Westminster, this can be a difficult procedural hurdle to overcome.

If a closure motion is lost then debate resumes and the clock continues to run down on the bill. If the closure motion is successful then the Speaker will call a vote on the Second Reading if one is needed.

If successful, the bill progresses on to its Committee Stage. If debate has not been brought to an end by 2.30pm then it is adjourned, and the continued Second Reading of the bill has to be rescheduled.

After the moment of interruption is reached, the Clerk will read out the titles of the other bills listed on the Order Paper which have not been debated and the Speaker will propose the Question on Second Reading if each MP bringing forward a PMB indicates that they still wish to move their bill.

If an MP objects then the Speaker will declare "Objection taken: Second Reading what day?". This invites the MP to nominate another sitting Friday for consideration of his or her bill.

Often, it is the government that objects to a bill and without government support a PMB will have no realistic chance of making progress.

But if no MP objects to the bill then it will pass Second Reading without debate and progress to Committee Stage. This is unusual but not unknown.

Only in exceptional circumstances might the committee stage be taken by a Committee of the Whole House.

If a PMB progresses beyond Second Reading it will generally be committed to a Public Bill Committee (PBC).

If a PMB has tax or spending implications (although these must not be the main purpose of a PMB) then the bill will require a money resolution (to permit the expenditure) or a ways and means resolution (to introduce a tax or charge) before it can be considered in committee. Only the government can bring forward such motions.

If the government declines to bring a motion forward then this thwarts the progress of a bill. The Public Bill Committee to consider the PMB can meet but it can not consider the clauses of the bill. It is permitted only to debate the bill on a motion to adjourn the meeting, which means debating the principles and the process but not the detail.

The Member sponsoring the PMB must provide the Selection Committee with the names of members willing to serve on the PBC. The Selection Committee will then formally nominate those members.

However, Standing Order No. 84A(5) permits the Selection Committee to nominate only one PBC to consider a PMB at any one time. As a result, if a number of PMBs pass through Second Reading stage, they can face bottlenecks as they wait in the queue for the PBC to become available. Only the government can table a motion to support the nomination of a second PBC to sit simultaneously to consider another PMB. (In the rare circumstance that the MP responsible for the first PMB was to tell the Selection Committee that they no longer wished to proceed with the committee stage for their bill, then a second PBC can be nominated; if subsequently desired, consideration of the first PMB cannot then commence until the proceedings of the second PBC have finished.)

Unlike the procedure for government bills, there is no provision for the taking of external evidence about a PMB from experts or members of the public at Committee Stage.

There is also no end date for a PBC: the time required for committee consideration of a PMB will be dependent on the nature of the bill and the level of interest in it.

It is at Report stage that PMBs frequently finally fall. As at Second Reading, opposing Members may again attempt to talk out the bill. Opponents can also table amendments designed to inhibit the purpose of the bill and take up time in debate. Supporting MPs may therefore need to move a closure motion one or more times during the debate, in order to keep the bill on track.

MPs can try to move amendments which were previously rejected or withdrawn at Committee Stage. Amendments to restore the original text of the bill by removing any changes made in Committee are also permitted.

If a bill has been considered by Committee of the Whole House then Report Stage is skipped.

As with government bills, Third Reading is usually a formality. No amendments to the bill are permitted: it is a final chance for MPs to pass or reject the bill in its entirety. Third Reading is often taken immediately after Report Stage and will involve only a short debate.

If the bill began its parliamentary passage in the House of Commons it will now go to the House of Lords for consideration.

Once a PMB has passed through the Commons it must be taken up by a Peer and pass through all stages in the House of Lords. Although the Lords may make amendments of detail and clarification, it is extremely rare for a Commons PMB to be defeated in the Lords.

Hansard Society (2022), Guide to Private Members' Bills (Hansard Society: London)