Grand National 2018: Cornelius Lysaght's ones to watch in Aintree race

A maximum field of 40 horses will line up for the Grand National

An estimated 600 million people worldwide will be following the runners as they race over Becher's Brook, the Canal Turn and other famous Aintree landmarks in Saturday's £1m Grand National.

Here's a look at those seeking Aintree glory, including a father and son, and husband and wife.

Will the Lion roar for Twiston-Davies & son?

Trainer Nigel Twiston-Davies says nothing would surpass winning a third Grand National with his jockey son Sam on board.

The horse concerned is Blaklion, whose stamina didn't last out the four and a quarter miles plus 74 yards as well as others when finishing fourth behind One For Arthur in 2017, having looked the likely winner.

Sam Twiston-Davies, 25, and 60-year-old father Nigel team up with Blaklion

Twiston-Davies Sr is the most successful Grand National-winning trainer among those currently holding a licence, having won with Earth Summit 20 years ago and Bindaree, whose 2002 victory caused plans to quit training to be shelved.

Sam has had eight attempts, the most successful of which came first time out when aged 17 and finishing fifth on stable stalwart Hello Bud behind winner Don't Push It in 2010.

"It would mean everything to us," said Twiston-Davies, who has compared Blaklion, winner of Aintree's Becher Chase over two-thirds of the Grand National course in December 2017, to Red Rum for the manner in which he skips around the examining course.

Verdict: Fences unlikely to pose any problems and obvious chance if stamina lasts out; did have a hard race when second at Haydock in February.

• Quiz: How much do you know about the Grand National?

Leading ladies - chasing a place in history

It is the oft-stated ambition of British racing to crown a female champion jockey - and soon - as policies aimed at encouraging women riders in the sport are pursued.

No single result would do more to aid the cause than victory in one of sport's greatest challenges for one of the three female jockeys - Bryony Frost, Katie Walsh or Rachael Blackmore - due to take part.

A string of high-profile successes, and her accompanying delight, has seen Frost - daughter of jockey-turned-trainer Jimmy Frost, who won the 1989 National on Little Polveir - steadily rise to prominence this season.

Although part of the high-flying stables of 10-time champion trainer Paul Nicholls, Frost's first Grand National mount - on Milansbar - is for trainer Neil King.

Katie Walsh was third on Seabass in 2012

In 2012, Walsh, sister of jockey Ruby, became the first female jockey in Aintree history to make the frame in the Grand National when third on Seabass, trained by her father Ted.

This time, as Walsh takes her sixth mount in the race, on Baie Des Iles, there is a further family connection as the seven-year-old grey mare is trained by her husband Ross O'Sullivan.

Blackmore, Ireland's champion conditional jockey (National Hunt apprentice) last season, takes part in the race for the first time when lining up on Alpha Des Obeaux, trained - like 2016 winner Rule The World - by Mouse Morris for the Gigginstown House Stud operation.

As race debutantes, Frost and Blackmore become the 16th and 17th women to ride in the race since Charlotte Brew became the first on Barony Fort in 1977.

Verdict: All are outsiders of the livelier sort, particularly perhaps - with conditions to suit - Baie Des Iles, whose Punchestown form last time looks strong.

Another one for Scotland?

A year on from One For Arthur providing Scotland with its first Grand National success since Rubstic in 1979 - and only second in history - the injured One For Arthur is missing, but compatriots Seeyouatmidnight and Captain Redbeard are seeking a Scottish encore.

It's been touch and go whether the Sandy Thomson-trained Seeyouatmidnight would make the line-up after bad weather, and the resulting cancelled fixtures, did its best to scupper the horse's chances of competing in just one race this season, which is now a qualifying factor.

However, a chase was found at Newbury for the 10-year-old, who was sold this week by his previous owner, Thomson's wife Quona, to race in the silks of Patricia Thompson - note the extra 'p' - who famously purchased the 1992 winner Party Politics just before that race.

The Berwickshire-based trainer, whose grandfather bred 1930s and 40s Grand National regular MacMoffat, once played rugby for Scotland B.

Speaking of a possible repeat for racing north of the border, he said: "We hadn't won the Grand Slam for about 60 years, and then along came two nearly in a row (in 1984 and 1990), so you never know."

One For Arthur, who won the Grand National in 2017, misses out this year through injury

Barely 20 miles away at Selkirk, Captain Redbeard's trainer Stuart Coltherd, also a sheep and cattle farmer, looks to add a second win over the famous Aintree fences to Tartan Snow's 100-1 success in the 2013 Foxhunters Chase. His jockey son Sam, 19, rides.

Meanwhile, if the Scots thought 38 years was a long time between drinks, Wales has been waiting even longer - 113 years since Kirkland in 1905.

Buywise, trained by Evan Williams, who saddled runners to finish in the first four every year between 2009 and 2013, is the flag-bearer this time.

Verdict: Seeyouatmidnight, a classy horse with conditions to suit, demonstrated his well-being when third at Newbury; Captain Redbeard has been in good form and has the potential to be a fairytale; Buywise has each-way credentials.

Gordon Bennett: Elliott's at it again

Perhaps jump racing's greatest story of recent years is the emergence of Gordon Elliott from journeyman jockey to, it could be argued, the sport's number one trainer.

This year alone, Elliott again pipped arch-rival Willie Mullins to be top trainer at March's Cheltenham Festival; a month later he won a first Grand National at home in Ireland; and he leads Mullins in the race to be champion trainer when the Irish season ends on 28 April.

Gordon Elliott has trained more than 200 winners this season

Now, with a challenge headed by three-time Festival winner Tiger Roll, part of Michael O'Leary's Gigginstown House Stud operation, Elliott's biggest backer, he looks for his second Aintree Grand National after his first with Silver Birch in 2007, the first time many had really ever heard of him.

For his part, Mullins' raid includes Cheltenham Gold Cup faller Total Recall, another of the favourites, plus Pleasant Company. With the Tony Martin-trained Anibale Fly, the Gold Cup third, also a leading contender, Ireland again demonstrates its current horse racing powerhouse status with three of the top four in the betting.

Verdict: Gold Cup runners Total Recall and Anibale Fly must be respected if they've recovered from their exertions; Pleasant Company was going menacingly well when all but grinding to a halt with a mistake at Valentine's on the second circuit in 2017.

Focus on safety

The horse welfare spotlight that was shone hard on Aintree for many years has tended to re-focus on Cheltenham of late after the deaths of six horses - three during one race - at the 2018 Festival.

Changes, including £1.5m spent on modifications to the famous Aintree fences after two fatalities in each of the 2011 and 2012 Grand Nationals, and the deployment of plastic frames, have been much applauded.

Although horses have suffered fatal injuries in other races staged on the Grand National courses, no runner in the big race itself has lost its life since.

However, managers insist they are not complacent and that they "do not stand still, reviewing everything on an annual basis".

A review is being carried out into safety at the Cheltenham Festival

Any other business

Horses for courses: the runners that finished from third down to seventh in 2017 are due to return for another go.

That's Saint Are, Blaklion, Gas Line Boy, Vieux Lion Rouge and Lord Windermere.

Also expected back is The Last Samuri, runner-up in 2016, but 16th of the 19 finishers last time.

If successful on Shantou Flyer, jockey James Bowen, who celebrated his 17th birthday in March, would be the youngest to win the race.

Bruce Hobbs was 17 years and three months old when steering Battleship to victory in 1938.

Welsh-born Bowen is already a record-breaking Grand National winner this season having become the youngest to triumph in the Welsh version at Chepstow in January on Raz De Maree.

James Bowen was just three years older than his horse when winning the Welsh National

Lightning to strike twice? When the Venetia Williams-trained Mon Mome became the most recent 100-1 winner in 2009, he'd been 10th the previous year.

Williams' Houblon Des Obeaux is also an outsider - 100-1 in places - and in 2017 he was… 10th.

With the BBC's brilliant John Hunt away on Commonwealth Games duty on the Gold Coast, Radio 5 live welcomes Aussie Matt Hill to lead our team of four commentators.

As the state of Victoria's principal caller, Hill - who has been part of the BBC team previously - is well used to the big occasions, having been at the helm for his first Melbourne Cup in November.

That said, the flat racing feature Down Under is less than half the distance, has a maximum of 'only' 24 runners and there are no obstacles for them to trip over.

• Pinstickers' guide to runners and riders

• More on the National: BBC radio 5 live preview, 21:00 BST, Wednesday