Two-time champion Andy Murray makes a welcome comeback in the Wimbledon singles when one of the sporting highlights of the British summer returns on Monday.

Serbia's Novak Djokovic is the favourite to defend his Wimbledon crown and win a record-equalling 20th Grand Slam men's title.

Romania's Simona Halep, who lifted the women's trophy in 2019, is fit to play after overcoming a calf injury.

However, Japan's four-time Grand Slam champion Naomi Osaka and Spanish great Rafael Nadal are missing from the grass-court Grand Slam.

There will be three British singles players seeded - Johanna Konta, Dan Evans and Cameron Norrie - for the first time since 1978.

Play starts on the outside courts at 11:00 BST on Monday, with Djokovic opening up Centre Court at 13:30 as Wimbledon tradition dictates.

The tournament is part of the government's Event Research Programme, which means it will operate at 50% capacity across the grounds, building to full capacity crowds of 15,000 on Centre Court for the finals weekend.

There are other changes this year as a result of the pandemic, including players having to stay in hotels rather than houses, as well as strict protocols for entry into the All England Club.

Will Djokovic equal Nadal and Federer?

Having won the past two Wimbledon men's singles titles, and claimed the Australian Open and French Open already this year, Djokovic is the overwhelming favourite to lift the trophy again on Sunday, 11 July.

Winning in Paris this month earned the Serb a 19th major title, giving him the opportunity to now move alongside long-time rivals Nadal and Roger Federer in terms of most all-time Grand Slam men's titles.

"I have put myself in a good position to go for the Golden Slam [all four majors plus Olympic gold in a single year]. I don't have an issue to say that I'm going for the title in Wimbledon. Of course I am," Djokovic, 34, said.

One of his potential threats has been removed by Nadal's withdrawal.

The 35-year-old Spaniard, a two-time Wimbledon champion, pulled out because he needs to "recuperate after a long clay-court season" and says it will help prolong his career.

There are also concerns about the fitness of eight-time champion Federer, who turns 40 in August.

Playing in his first Grand Slam for 16 months because of a knee injury which required two surgeries, the Swiss reached the third round of the French Open. He then withdrew before his last-16 match to protect his body, having also said Wimbledon was his top priority this season.

A return at the Halle Open last week ended in a second-round defeat by 20-year-old Canadian Felix Auger-Aliassime.

What about the younger generation? No man other than Djokovic, Federer, Nadal and Murray has won the singles title since Australia's Lleyton Hewitt in 2002.

Greece's Stefanos Tsitsipas, 22, is the second-leading player behind Djokovic on the ATP Tour this year, although he could not stop the Serb fighting back from two sets down in the Roland Garros final.

Italian Matteo Berrettini, a big server with a potent forehand, looks to have the game to do well and the 25-year-old won the Queen's title last weekend.

Neither player has yet reached the Wimbledon quarter-finals, though. The only one of the other top eight seeds apart from Djokovic and Federer to have done so is Spain's Roberto Bautista Agut, who was a semi-finalist in 2019.

How fit will Halep be? And will Serena win that elusive 24th major?

After being denied the chance to defend her crown last year, 29-year-old Halep finally has the opportunity now.

That looked far from certain after she left the court at May's Italian Open in tears with a calf injury that subsequently ruled her out of the French Open. How fit the Romanian second seed is remains to be seen.

Seeing another different name on a women's Grand Slam trophy would not be a surprise, with 13 different winners in the past 17 majors.

Japan's Naomi Osaka has won four of those titles but is still taking a break from the sport, having revealed at the French Open that she has been suffering from depression.

Serena Williams lost to Halep in the 2019 final - and finished runner-up to Germany's Angelique Kerber the year before - and once again goes for a record-equalling 24th Grand Slam singles title.

Matching the number won by Australian Margaret Court has so far proved elusive for the American, who turns 40 in August, since returning from maternity leave three years ago.

But the Wimbledon grass - where she is a seven-time champion - seems the place most likely to yield another major.

Australian world number one Ashleigh Barty is the leading player on the WTA Tour this year and has already won three titles. At Wimbledon the 25-year-old will be playing on what she describes as her favourite surface, although she has not played a tournament since Roland Garros because of a hip injury.

Poland's Iga Swiatek, 20, is one of six former Grand Slam champions among the top eight seeds and won the junior title at SW19 in 2018, while Czech Barbora Krejcikova is seeded 15th as she looks to back up her surprise French Open triumph.

Murray back as Konta, Evans & Norrie lead British hopes

When 2013 and 2016 champion Murray limped off Centre Court following his 2017 quarter-final defeat by American Sam Querrey, few would have predicted the Scot would not play in the singles again until four years later.

The hip problem that had bothered him throughout the tournament resulted in a first surgery in January 2018 and then another in January 2019.

The second - a resurfacing procedure which means Murray has a metal hip - came shortly after he tearfully announced at the Australian Open he thought the problem would force his retirement.

While the surgeries have derailed the three-time Grand Slam champion's career, they have not ended it.

Murray made his singles comeback at Queen's last week following a niggling groin injury, losing to top seed Berrettini before focusing on his preparations for Wimbledon.

"The reason why I'm still playing is because I enjoy it and I don't see any problem with that," he said.

"I'm not offending anyone and it's not hurting anyone. I like it."

Evans, 31, has become the British men's number one in the absence of Murray and is seeded 23rd as he looks to reach the second week in SW19 for the first time.

While 28th seed Konta has a rich pedigree, having reached the 2017 semi-finals, the 30-year-old has struggled for form and fitness in the past couple of seasons.

A niggling knee injury continues to have be carefully managed and led to Konta pulling out of Eastbourne last week, shortly after she won the Nottingham title.

Perhaps Britain's best hope comes in the shape of 25-year-old Norrie, who finished runner-up at Queen's last weekend.

A fantastic year has seen the South African-born, New Zealand-raised left-hander, who pledged allegiance to Britain in 2013 because of his Welsh and Scottish parents, climb to a career-high ranking of 34 and he will be seeded at a Grand Slam for the first time.