|Venue: Cheltenham Racecourse Date: 13-16 March|
|Coverage: Full coverage on BBC Radio 5 live; continued on BBC Radio 5 live sports extra; live text updates on BBC Sport website|
Buveur D'Air retained the Champion Hurdle title with a thrilling victory from Melon at the Cheltenham Festival.
The 4-6 favourite held on by a neck under jockey Barry Geraghty to give record-breaking trainer Nicky Henderson a seventh victory in the race.
Buveur D'Air was passed by Melon on the uphill finish before battling back to triumph from the 7-1 shot, with 25-1 chance Mick Jazz in third.
The winner's stablemate Charlie Parcs set a searing pace in the testing conditions and was followed by 2015 winner Faugheen before they both faded.
Footpad was a brilliant winner of the Arkle Chase after Ruby Walsh steadied his Willie Mullins-trained mount following an early blunder.
And jockey Lizzie Kelly scored her first Cheltenham Festival victory as 5-1 favourite Coo Star Sivola, trained by her stepfather Nick Williams, landed the Ultima Handicap Chase.
Kelly is the first professional female jockey to ride a winner at the Festival. Eleven other women who triumphed previously did so under amateur status.
- Cheltenham analysis and tips: 5 live podcast
- Full racecards and results from day one of the Festival
- BBC coverage details of Cheltenham Festival 2018
'One of the best rides I've ever seen'
Buveur D'Air became the sixth horse to win the two-mile Champion Hurdle more than once, but the seven-year-old was made to battle for victory.
Geraghty always had his horse in the slipstream of the early pacesetters, but it was Paul Townend on the well-backed Mullins challenger Melon who posed the biggest threat.
The two hurdlers went head to head up the home straight, roared on by a bumper crowd, before Buveur D'Air got the better of the tussle.
"That was a great ride from Barry Geraghty," said jockey Tom Scudamore, who was summarising for BBC Radio 5 live.
"You talk about being a goalhanger in football and the key to that is knowing the positioning to go and do that.
"It would have been very easy for Barry to allow Buveur D'Air to jump the last and push too hard but he didn't and he has earned his keep. It was one of the best rides I've ever seen."
It was a seventh Champion Hurdle for Henderson, and also for owner JP McManus. The Festival's all-time leading trainer has previously won with See You Then (1985, 1986, 1987), Punjabi (2009) and Binocular (2010).
Henderson, recording his 59th Festival victory, said: "It was a brilliant race. They were two very brave horses with two brave jockeys. This was a proper race and he showed his class."
Geraghty was ruled out of last year's Festival after puncturing a lung and breaking six ribs in a fall.
"I missed last season and it was a long year, but I can't complain. I thought he was coming to beat me, but my fella is battle-hardened and tough as nails," said the jockey.
by Cornelius Lysaght, BBC horse racing correspondent at Cheltenham
I think, ideally, we like our champions to bolt up, and this was very tight as Buveur D'Air joined the likes of Hardy Eustace, Istabraq, See You Then and Sea Pigeon as a back-to-back champion.
His trainer quite reasonably put the narrow margin down to the quality of Melon, plus that after three easy races this was the first time the seven-year-old had really been tested - and, of course, he did come through it.
There will be talk of retirement for former Festival stars Faugheen (6th) and Yorkhill (pulled up), and if that's the decision, they go out with heads held high.
Footpad thrills Cheltenham
In the Arkle Chase, Footpad made a serious early error but Walsh bided his time as Petit Mouchoir and Saint Calvados battled it out at the front and came through for an impressive 14-length victory on the 5-6 favourite.
Jockey Walsh, who had only returned to racing from a broken leg five days ago, has more wins than any other rider at the meeting and this took his career tally to 57.
"It made the hairs on the back of my neck stand up," said Walsh, 38.
"It is wonderful. It is great to be back. It has been a long winter and you wonder if it is all worth it and then you get a winner here and you remember it all over again. The leg was all right. Physical pain can be managed."
Mullins said Footpad could be a future Cheltenham Gold Cup contender.
Walsh made it 58 when winning the OLBG Mares' Hurdle for Mullins on Benie Des Dieux.The 9-2 chance beat outsider Midnight Tour (33-1) as 1-2 favourite Apple's Jade could only finish third in the race she won last year.
Mullins enjoyed a 54-1 opening-day treble with his son Patrick winning the National Hunt Chase on Rathvinden.
On a day with several tight finishes, Rathvinden just edged out Ms Parfois to win the four-mile National Hunt Chase.
There was some sad news after the race as it was confirmed Mossback, trained by Gordon Elliott, had to be put down after suffering an injury.
Report To Base, trained by Evan Williams, suffered a fatal fall in the following race.
Kelly cool on Coo Star Sivola
Victory for Kelly, the first woman to ride a Grade One winner over jumps - on Tea For Two in 2015 - was a form of Festival redemption.
She left the meeting dejected last year after being unseated from Tea For Two at the second fence after lining up as the first female rider in the showpiece Gold Cup for 33 years.
A decision to partner Diable De Sivola rather than eventual winner and stablemate Flying Tiger in the Fred Winter Hurdle also backfired.
But the 24-year-old bore a wide smile this time thanks to a thrilling success in the Ultima Handicap Chase, edging out runner-up Shantou Flyer by just a neck.
"That uphill finish was so long. I can't believe it. I'm speechless," she said.
"Although I had a horrendous Cheltenham last year, you learn from that. I genuinely had written off the idea of me having a Festival winner. This is the cherry on top. I am delighted."
Kelly, who is also working as a BBC Radio 5 live pundit this week, had been confident of her mount's chances.
Asked for her selection in a BBC Sport website preview, she said: "It would be wrong to not pick my own ride Coo Star Sivola. He's sure to like the trip and ground. I'm very excited to be riding him in this race I think it's my best chance of a winner this week."
The meeting began on the wettest ground for 36 years after persistent rain in the build-up, with the going described as heavy, soft in places.
But the clouds lifted and the sun shone as a crowd of around 65,000 gave out the traditional 'Cheltenham roar' for the start of action at the Gloucestershire track.
And it was local trainer Tom George - based around 15 miles away at Slad - who triumphed in the opening Supreme Novices' Hurdle as Summerville Boy (9-1) denied Kalashnikov in a thrilling finish.
Favourite Getabird, for the Walsh-Mullins combination, faded after leading from the front and the winner - ridden by Noel Fehily - got up on the line after surviving some jumping errors including a bad mistake at the second last.
Former England striker-turned trainer Mick Channon celebrated a first Festival winner when the bottom weight Mister Whitaker (13-2) won the concluding Close Brothers Novices' Handicap Chase.