Green Party: How might new job-share leadership work?

Caroline Lucas and Jonathan Bartley have been elected co-leaders of the Green Party in England and Wales, in what they say is a "pioneering" job-share arrangement.

The two gave a joint acceptance speech in which they said their election on a single ticket showed the party was not afraid to be different and was not bound by tradition.

As the party's first and sole MP, Ms Lucas is one of the most familiar figures in British politics while Mr Bartley is relatively unknown outside Westminster.

But what do we know about the duo and how they will work together?

Caroline Lucas

It is second time around for Caroline Lucas who having led the party between 2008 and 2012, will now take the helm again - this time in tandem with Mr Bartley.

Ms Lucas made history when she became the party's first MP in 2010 taking the seat of Brighton Pavilion from Labour. She was re-elected in 2015 with an increased majority of nearly 8,000.

At Westminster, the 56-year old has raised the party's profile with her opposition to the so-called "bedroom tax", the benefits cap, the renewal of Trident and the Sun's Page 3 while she hit the headlines in 2013 for different reasons when she was arrested during an anti-fracking demonstration.

The Spectator named her "newcomer of the year" in 2010 and, although a lone voice on many issues, she has become a widely respected figure across the House.

Ms Lucas, who was an academic before entering politics and has also served as an MEP, took many by surprise when she stood down in 2012.

At the time, she said she wanted "to give other people the opportunity to get well-known, to have some profile in the party, hopefully to use that to get themselves elected as well".

She was replaced by Natalie Bennett but the new leader failed to be elected to the Commons in 2015 despite boosting her profile by participating in the leaders' debates at the last election.

Labour's move to the left under Jeremy Corbyn has also raised concerns that the party's vote could be squeezed.

Ms Lucas has courted controversy by floating the idea of an electoral pact with Labour and other progressive parties to take seats from the Conservatives in 2020.

Although Ms Lucas is respected by the current Labour leadership - to the degree that she was at one point tipped for a job in Jeremy Corbyn's shadow cabinet - the idea of a pact has been dismissed by Labour, and many Green activists are wary.

Jonathan Bartley

Jonathan Bartley is the Green Party's spokesman on work and pensions who, according to their leadership manifesto, has much in common with Ms Lucas including "considerable experience of campaigning and winning".

Active in the Green Party in south London for about five years, the 45-year-old stood for the party in the recent London Assembly elections but failed to win a seat.

A year before that, he stood as a general election candidate in Streatham, coming fourth.

As a student at the London School of Economics in the early 1990s, Mr Bartley is believed to have had Conservative leanings.

He is reported to have volunteered for John Major in 1995 when the then prime minister faced a challenge to his leadership from John Redwood.

He founded the think tank Ekklesia in 2002 - only standing down as a director earlier this year - and became a commentator on issues of faith, religion and public policy.

Mr Bartley first rose to national attention as vice-chairman of the Yes to Fairer Votes Campaign during the 2011 referendum - in which the Greens were a prominent voice.

He was a spokesman for the organisation in its ill-fated effort to persuade the public to ditch the current first-past-the-post electoral system in favour of the alternative vote.

But he is perhaps best-known for his public confrontation with David Cameron during the 2010 general election campaign during which he raised his concerns about the treatment of disabled children in the education system.

Mr Bartley told the then prime minister about the two-year struggle he had faced to get his son Samuel into a local school and remonstrated with Mr Cameron about plans to end the bias towards inclusion of children with special needs in mainstream schools.

Mr Bartley, who is married with three children, is a direct descendant of the prison reformer Elizabeth Fry and is a drummer for the Mustangs soul group.

How the arrangement might work?

As David Owen and David Steel can testify, joint leadership of a political movement is not necessarily a bed of roses.

The two men headed the SDP-Liberal Alliance during the mid-1980s and were mercilessly satirised by Spitting Image in the run-up to the 1987 election - with Mr Steel being characterised as a midget in Mr Owen's pocket.

Spreading the leadership burden is not entirely alien to the Green Party, which historically shied away from having a single figurehead, relying instead on having what they described as two principal speakers.

The job-share ticket recalls this arrangement - which lasted until 2008 - and has echoes in the Scottish Green Party, which is led by two co-convenors.

Although it is unclear how the approach will work in practice, it has been suggested that Ms Lucas will lead the party's parliamentary and campaigning efforts in areas such as fracking and the EU, while Mr Bartley will focus more on organisation and policy.

With his background in communications, Mr Bartley is also expected to take on some of the party's media duties as well as trying to differentiate the party's pitch on the economy, social issues and public services.