Olympics: Who will be in the Great Britain team at Rio 2016?

More than 30 of the Britons who won medals at London 2012 were aged 25 or under.

Fifteen of those won gold. How many of them will be back to defend their titles in 2016 at the Rio Olympic Games, and who else might come through the ranks to join them?

A week is a long time in sport, never mind four years. But here, BBC Sport takes an early look at some names in the frame for future Olympic fame.

Returning heroes

Six of the 12 British Olympians who won more than one medal at London 2012 were younger than 26.

Laura Trott, 20, and boyfriend Jason Kenny, 24, were both double Olympic champions in the velodrome, Andy Murray, 25,took tennis gold and silver, gymnasts Louis Smith, 23,and Max Whitlock, 19,both picked up two medals, and Rebecca Adlington, 23,won double bronze in freestyle swimming.

It would be risky to bet against any of them returning for Rio. Trott, in particular, has the chance to establish a legacy to match Sir Chris Hoy's record medal haul over the next decade, having dominated her team pursuit and omnium events in recent years.

Adlington has some thinking to do after losing both of her Olympic titles, particularly following the stunning performance of American 15-year-old Katie Ledecky over her favoured 800m distance. Smith has suggested younger gymnasts may prove better all-rounders and push him out of the 2016 gymnastics team.

But you can expect Whitlock to be a bedrock of that squad if he maintains his progress, while Trott and Kenny should have at least two more Olympic outings left in them, if not more. Murray will certainly hope to defend his singles title in Rio.

Of course, 25 is something of an arbitrary barrier. In many sports, you can just as easily win a medal in your 40s or 50s as your teens. Many of GB's gold medallists can be expected to fight for their place, if not retain their title, in four years' time - think of the likes of Jess Ennis, 26,and Mo Farah, 29, plus many of the GB rowing team.

To take an example from the opposite end of the spectrum: Nick Skelton is 54, has come back from a broken neck and a hip replacement, and now needs work on his back - but the team showjumping champion plans to return.

Already on their way

Plenty of likely candidates for Rio 2016 have already broken into the team at London 2012, even if they didn't grab the headlines.

The most obvious of these is Adam Gemili, the world junior champion over 100m, whose time of 10.06 seconds in the Olympic semi-finals saw him narrowly miss out on a place in the final alongside the likes of Jamaican winner Usain Bolt and his team-mate Yohan Blake.

Gemili, still only 18, has already been hailed by US rival Tyson Gay as a man with the potential to become one of the greatest in history. By Rio, we will know a lot more about what the former footballer can achieve on the track.

Nineteen-year-old Katarina Johnson-Thompson (heptathlon or long jump) and 20-year-old hurdler Andrew Pozzi are others whose names were lower down the 2012 card but could top the billing in Rio.

Andrew Osagie, the 800m runner, finished last in his final as David Rudisha stormed home in a new world record, but the Briton ran a personal best that would have won gold at any of the three previous Olympics. He will be 28 in 2016.

In contrast Olympic triathlon champion Alistair Brownlee occupied every headline going with his stunning win but will face renewed pressure from younger brother Jonny in Rio.

The two look set to dominate their sport for years to come, but 22-year-old Jonny may yet have it in him to surpass his 24-year-old sibling in time for Rio, having taken bronze behind Alistair in Hyde Park.

In gymnastics, Rebecca Tunney made her Olympic debut as the youngest member of Team GB at the age of 15, looking assured and unfazed in the women's all-around final. She will spend the next four years increasing the difficulty of her routines although, in a sport with a phenomenally high turnover rate as new gymnasts come on the scene, she already faces a battle to keep her place in the British team.

Fencer James Davis impressed as Britain valiantly scrapped to a narrow defeat by world number ones Italy in the men's team foil event, and he could be joined by world junior epee champion Philip Marsh in Rio.

Teenager Harry Martin somehow managed to have a decent game for the GB men's hockey team as they were drubbed 9-2 by the Netherlands in their semi-final and is one to watch, while rowing trio Constantine Louloudis, George Nash and Will Satch all picked up bronze at Eton Dorney and will look to upgrade that in Brazil.

Swimming was a disappointment for Britain at their home Games, and now the search is on for future stars. Siobhan-Marie O'Connor, the 16-year-old breaststroke swimmer from Bath, may be one of them if she can improve her race strategy. Diver Jack Laugher struggled in his 3m competition and finished 27th but he will only be 21 by the time of Rio; Tom Daley, of course, will be just 22 himself.

New faces

Some of the GB stars at Rio 2016 could be in sports entirely new to the Games.

British teams will fancy their chances at medals in rugby sevens, introduced to the Olympic programme for the first time, with Michaela Staniford a name to remember as the 25-year-old captain of the current England women's team.

Kiteboarding replaces windsurfing for Rio and Steph Bridge, a four-time world champion in the sport for Britain, has already seen her profile rise as a result. If windsurfing wins its appeal against losing its place, Izzy Hamilton could benefit. The pro windsurfer is also taking up kiteboarding with a view to reaching Rio, no matter which of the two is included.

Elsewhere in sailing, 22-year-old Katrina Hughes - who lost her battle for a place in the women's 470 boat to Hannah Mills and Saskia Clark, this time - will be back and raring to go alongside partner Penny Clark for 2016.

A crop of gymnasts are preparing to emerge from the increasingly successful British junior production line. European junior champions Frank Baines and Nile Wilson are two leading lights on the men's side while Youth Olympic trampolinist Nathan Bailey is hoping to star at 2016. Ellie Downie, younger sister of 2008 Olympic gymnast Becky, is just 12 years old now but will be 16 and could have reached her peak by the time of the next Games.

Cycling has a seemingly endless conveyor belt of talent to raid for 2016. Names like Lucy Garner and Simon Yates, both already junior world champions in their short careers, could be firmly established in senior circles well before then.

Other names waiting in the wings for Rio include boxer Chantelle Cameron, eventer Laura Collett and modern pentathletes Freyja Prentice and Jamie Cooke, the latter tipped by his coaches as a future world champion.

Rowers Pat Lapage and Mike Evans, and Michael Eilberg with Woodlander Farouche in dressage, will also hope to be in Rio.