When Zersenay Tadese's name appeared on a full marathon entry list for the first time 12 months ago many in the distance running world held their breath in anticipation.

The Eritrean had one of the quickest half marathon times ever and was a triple world half marathon champion. He was also an Olympic 10,000m bronze medallist and a former world cross country champion.

So it's hardly surprising that some predicted he would be the quickest marathon debutant ever and would challenge the likes of Olympic medallists, Sammy Wanjiru, Jaouad Gharib and Tsegaye Kebede for the London title.

But Tadese's marathon debut in London last year turned out to be one to forget. As Wanjiru and co scorched through the city at world record pace, Tadese hung on gamely for 19km until the strain got too much and he dropped back from the leaders, later dropping out altogether at 35km.

Twelve months later Tadese is back, and so is the anticipation. Not least because the 28-yea-old added a fourth world half marathon title to his CV in Birmingham last October, and then, in Lisbon last month, smashed Wanjiru's world record clocking 58:23.

Not bad considering he entered that race merely as warm-up for his second London Marathon outing.

"Lisbon was good but it was just preparation for London," he said. "You could say it was perfect preparation."

So what has he learned since last year?

"Last year I was sick after running in the World Cross Country Championships in Amman," he said. "That was a mistake. Now I am in shape because I have been training only for the London Marathon.

"I really think I'll be running well on Sunday. I'm at my best."

Quite how good his best can be has been the subject of speculation among marathon experts.

Wanjiru was Tadese's predecessor as half marathon world record holder and the 23-year-old has had a brilliant marathon career. The Kenyan has broken 2:06 three times and ran his best of 2:05:10 when he won in London last year. He's also, of course, the Olympic champion.

Tadese is, sensibly, given his experience last year, reluctant to make rash predictions about the race on Sunday, saying only, "I'm very happy to be here. I'd like to thank the organisers for inviting me again."

Of course, Wanjiru and his fellow Kenyans - world champion Abel Kirui, and world all-time number two, Duncan Kibet - are not the only opponents Tadese needs to fear. Gharib and Kebede, who finished third and second respectively in 2009, are both seeking their first London titles this year.

At 37, Gharib, the 2003 and 2005 world champion, believes he still has much to prove as a marathon runner. "There are so many reason why I keep going," said the Moroccan who will make his sixth London appearance on Sunday.

"I started running a bit later in life, at 22 and I have looked after my body. But running is also my hobby. It's something I've always enjoyed so I never get tired or fed up with it, and I enjoy training."

Kebede is much less experienced than Gharib but his London debut last year was at the other end of the scale from Tadese's. The 23-year-old mounted a fierce challenge to the Kenyan dominance which has prevailed since Evans Ruto's victory in 2004 as he hung on to Wanjiru until the final mile and finished just 10 seconds back in a personal best of 2:05:20.

In Fukuoka last December he lowered that PB by two seconds. As the lone Ethiopian in the men's race, he will carry his nation's hopes again, and Wanjiru, for one, tips him as the man to watch, saying, "He has experience of the course now. I expect him to be strong."

Kebede also believes he's in better condition this time. "My preparation has been very good," he said. "I feel confident I will have a good result this year. I'm in better shape than last year and will be better prepared to win."

He certainly has no fear of Wanjiru, whatever the Olympic champion's record and reputation. "You cannot run alone in this race," he said. "To win you have to run with someone. So with runners like Sammy around it encourages me to push on and to do better."

This Sunday, Zersenay Tadese will be hoping to do better too. It could be quite a tussle.