Pakistan have a theoretical chance of emerging as the top-ranked Test side during the ongoing summer tour of England – with a little help from Australia, and ironically, arch-rivals India.

Currently ranked third on the International Cricket Council’s (ICC’s) rankings for the top 10 Test sides – one notch behind India – Pakistan last held the top slot for only a brief period 28 years ago.

For them to be the best again, merely beating England in England is not going to be enough to dislodge Australia from the pinnacle, where Steven Smith’s men have been roosting for the past four months.

A lot also depends on variables in distant Sri Lanka, where Australia are currently playing the first of a three-Test series.

Read: Pakistan will bounce back, says Inzamam

Pakistan cannot hope to become the number-one side – even if they defeat England – unless the mighty Australians register a series loss to a relatively weaker Sri Lankan squad.

The scenario

At the moment, the four top sides are simultaneously jostling for the number-one slot: Australia (with a rating of 116), will want to retain their spot, while India (112), Pakistan (111) and England (108), will try to wrest it from them.

(After every Test series, the two competing teams receive a certain number of points based on a mathematical formula. The rating is the nearest whole number arrived at after a team’s points have been divided by its match/series total).

Australia are numero uno by a long shot, and a series win over Sri Lanka will help them maintain the status quo, irrespective of what plays out in the England-Pakistan series, or the India and West Indies, currently underway.

They will have to win 2-0 or better against seventh-ranked Sri Lanka to ensure it does not go below its current 118 points. A 1-0 result in Sri Lanka’s favour will see Steve Smith’s side slip to 111 points.

India at the second spot with 2,238 points – 1,527 behind Australia – are in a position similar to that of Pakistan: the top slot depends on extraneous factors as much as their own performance.

To regain the number-one Test side status that they ceded to Australia this February, India must not only whitewash West Indies, but also hope for Australia to lose to Sri Lanka, and the England-Pakistan series to end in a draw.

Read: It is England’s method versus Pakistan’s madness now

A 3-0 margin or better will help it stay at 112, and even a 3-1 or 2-1 will see it slip to 110 points.

On the other hand, a 1-3 loss by India will see them dropping below the 100-point mark.

Breathing down their backs are the Pakistanis with 2,227 points, who would want to wrap up the next two Tests, having won the first and lost the second.

And if they do manage do that and the Australia lose to Sri Lanka, the outcome of the West Indies-India series will have no bearing; Pakistan will reach the number-one slot.

This, because West Indies are placed four spots below England, and a series win over them by the second-ranked India will bring less bonus points than a series win by the third-ranked Pakistan over England.

This difference becomes crucial as only 11 points separate India and Pakistan now.

Meanwhile, England are fourth on the rankings – with 3,872 points, but from 16 more matches than either Pakistan or India, and four more than Australia.

Their chance of claiming the top spot is slightly tougher than Pakistan’s. Like Misbah’s team, they not only have to win the next two games and hope for an Australian debacle, but they also need West Indies to beat a much stronger Indian side at least once.

The ranking story

The current Test ranking – notionally called the ICC Test Championship – is calculated on the performances of the top 10 Test playing teams including Bangladesh and Zimbabwe since 2003.

In the 157 months since then, three teams have primarily held sway: Australia, (number one in three stretches totalling 81 months or over 51 percent of the time), South Africa (thrice, totalling 42 months) and India (twice, totalling 21 months).

Read: Cold weather and England set to come down hard on Pakistan

England also featured once – for an even 12 months from August 2011 to August 2012.

The Pakistanis have never been the number-one Test team under the active ranking system effective since 2003.

However, they did feature as a top team about three decades ago. It was only once, and that too for only two months in the pre-ranking period of Test teams.

The ICC recently applied its current rating system to results going back to 1952, prior to which the data available is deemed insufficient for calculation purposes due to the infrequency of matches and the small number of competing teams.

In the 1952-2003 period, Pakistan was retrospectively rated the top side during August-September 1988.

Interestingly, even in this 51-year period, the Indians enjoy a better record, having being adjudged top side over three time spans totalling 24 months: April 1973-June 1974 (15 months), September 1980-February 1981 (six months), and September 1995-November 1995 (three months).

There is always scope for redemption, but it is up to Misbah-ul-Haq’s team to rewrite their ranking.

The question is: will they take up the challenge?