The UK is not obliged to have a deputy PM - but John Prescott's legacy shows it's a job worth having
"Giant", "titan", "the Labour Party could never have won three consecutive terms without John".
The praise heaped on John Prescott who died on Wednesday is proof that the job of deputy prime minister is worth having.
It may be more influential than the vice presidency of the United States, famously dismissed by one VP, John Nance Garner, as "not worth a bucket of warm piss".
Vice presidents are mandated by the US constitution. They are "only a heartbeat away" from assuming the Oval Office if the sitting president dies suddenly - as happened when Lyndon Johnson was sworn in immediately after John F Kennedy's assassination - or resigns, as with Richard M Nixon and Gerald Ford.
There is no guarantee that they will be elected in their own right after years as a frustrated and overlooked number two: George HW Bush and Joe Biden made the transition to the White House at a subsequent election, while Al Gore and Kamala Harris did not.
The UK is not obliged to have a deputy prime minister (DPM). There have only been nine formally acknowledged as such in British political history.
Nonetheless, some of the most influential politicians of modern times have been DPM including Clement Attlee, Michael Heseltine, John Prescott, Nick Clegg, and now potentially Angela Rayner.
Then there is the roster of major figures, critical to their governments' successes who have been de facto DPMs in all but name, such as Herbert Morrison, Anthony Eden, Rab Butler, Geoffrey Howe and Willie Whitelaw.
Margaret Thatcher is said to have declared: "Every prime minister needs a Willie."
As befits an office that Labour's Prescott occupied with such distinction, the first designated DPM was Labour's undisputed hero Attlee.
The Conservative prime minister Winston Churchill wanted his Labour deputy in the wartime coalition government to be officially recognised.
Attlee was billed as DPM in Hansard, the official parliamentary record, but King George VI complained there was no such thing under the constitution.
Monarchs can be jealous of their notional right to choose the prime minister. Attlee went on to become prime minister in his own right, ousting Churchill in the 1945 General Election.
The title of DPM was then in abeyance for the next 50 years until prime minister John Major brought it back for Michael Heseltine, who had helped him win a leadership challenge.
"Hezza" was already a veteran cabinet minister whose own earlier efforts to lead the Conservative Party had failed. With the additional title of first secretary of state (FSS), he relished the opportunity to chair cabinet committees and argue for closer ties to the EU.
By the 1990s, the Labour Party had started electing both its leader and deputy leader. Prescott stood for both jobs.
While he was comfortably defeated by Tony Blair for prime minister, he beat Margaret Beckett for deputy. Prescott became DPM almost automatically when Labour took power in 1997.
He stayed in the job for 10 years as the rough to Blair's smooth - a crucial bridge from the old Labour's union-dominated politics to New Labour's big tent and a troubleshooter in the rivalry between Blair and Gordon Brown.
Prescott resigned with Blair in 2007. Harriet Harman was elected deputy Labour leader but did not receive the formal title of DPM.
Read more on John Prescott:
John Prescott, a pork pie and me
Labour's pugnacious stalwart who pulled no punches
What has Labour learned from Prescott?
It returned in super-charged form when the Conservative David Cameron formed a coalition government with the Liberal Democrats in 2010.
Since Nick Clegg commanded the swing votes which the government needed to make laws, he was the most powerful DPM yet, as he explained "we had to create a sort of two-headed, bicephalous way of making decisions".
The Conservatives won power on their own in 2015 and had no DPMs until 2021. Cameron made do with George Osborne as just FSS.
Theresa May gave the same title to Damian Green in the post-Brexit referendum chaos. When Green resigned due to scandal, the then Chancellor of the Duchy of Lancaster David Lidington was known as "the de facto deputy prime minister" without being made either FSS or DPM.
As the turnover of Conservative leaders accelerated, Boris Johnson made Dominic Raab FSS and then upgraded him to DPM.
Liz Truss also appointed Therese Coffey as her short-lived DPM. Rishi Sunak then brought back Raab as DPM, before Oliver Dowden replaced him.
None of these deputies were paid any extra above their ministerial salaries. They enjoyed no special authority or powers and no guarantee that they would take over if the prime minister was incapacitated or away - although Raab was installed temporarily when Boris Johnson was in hospital with COVID.
The opportunity to stand in at PMQs when the prime minister is away has been downgraded now that the leader of the opposition sends in a deputy as well.
Rayner and Dowden both seemed to enjoy their oft-repeated "Battle of the Gingers". Kemi Badenoch says she plans to vary the substitutes she sends in to face the DPM.
No DPM, FSS or "de facto" since Attlee and Eden in the 1950s has gone on to be prime minister.
Read more from Sky News:
Alex who? Have the Tories found a new rising star?
Hancock: NHS was within 'hours' of running out of PPE
The most successful DPMs - such as Heseltine and Prescott - were more colourful personalities than their bosses and became popular household figures while loyally supplying the heart to their governments.
They also managed to drive through their most treasured political priorities: Heseltine and Clegg both held back the Conservatives from calling a referendum on EU membership.
Prescott was a driving force for progressive Labour Party reform, for devolution, and in committing the UK to the Kyoto Protocol on climate change.
Intriguingly, Labour now have an elected deputy leader and DPM who seems to have much in common with Prescott.
Rayner has also climbed up from a troubled working-class background via the trade union movement.
She hails from the North of England and has a similarly blunt and idiosyncratic way of expressing herself in contrast to the north London lawyer style of her leader.
She too finds herself a member of a triangle made up of PM, DPM and chancellor of the exchequer. She has described herself as "John Prescott in a skirt".
Rayner has a great role model as DPM to emulate - she may even have the time and space to surpass him in importance.