Dean Macey has a very narrow lead after the completion of the first day of the decathlon

The British athlete ran a personal best to win the 400m and gain a one point lead over his rivals.

His time of 46.21 seconds won his heat from Erki Nool and Tomas Dvorak.

His tally of 998 points puts him ahead of those two, although he admitted afterwards that both are capable of better second days than him

"I'm happy with the high jump, because its over eight years since I jumped over 2.13!" said Macey.

Macey needed a pain-killing injection before he competed in the 400m, admitting afterwards: "It was touch and go that I would compete at one stage.

"But I'll carry on tomorrow (Tuesday) though it is going to be very close."

He also admitted that he had not actually had a high jump since the Olympics in Sydney.

The silver medallist from 1999 says he is now aiming for a tally of 8848 over the ten events.

He had already cleared a personal best 2.15m in the high jump to notch 944 points and overtake Estonia's Nool, who could only clear 2.06m

Macey's main rival Dvorak failed on his attempt at 2.03m but kept a comfortable cushion in the standings with only the 400m remaining on the first day.

Macey began his campaign impressively with a strong 100m but failed to produce his very best in the long jump and shot put.

Dvorak, meanwhile, produced an awesome leap of 8.07m in the long jump before throwing out to 16.57m to move clear of the field.

Macey, who won his 100m heat in a time of 10.72 seconds, earning him 924 points, claimed third place in that event.

The 23-year-old began nervously and made a false start, but got away at the second time of asking.

Fast start

And his run was just three-hundredths of a second outside his lifetime best, set in the worlds in Seville two years ago.

Macey, competing in his first decathlon since the Sydney Olympics, punched the air when he saw his time on the stadium scoreboard.

Erki Nool won the second heat in 10.60secs and led the field with 952 points after the first event.

Current world champion Tomas Dvorak finished second in 10.62secs.

But world record holder Roman Sebrle could only manage fifth in the second heat with a time of 10.91secs.

The final heat was won by Portugal's Mario Anibal, who ran a personal best time of 10.84secs, which earned him 897 points.

Macey then moved on to the long jump where his first and only legal jump of 7.59m earned him 957 points.

Massive leap

Subsequent attempts to improve upon that distance were undermined by two fouls.

Defending world champion Dvorak jumped a massive 8.07m in his first attempt earning him 1,079 points.

Nool, leading after the 100m, managed a best jump of 7.63m, which earned him 967 points and into second spot.

Roman Sebrle, the current world record holder, bounced back after his disappointing 100m.

He jumped 7.67m with his first effort, but was timed-out while preparing for his second jump and ran through the take-off board with his final attempt.

The shot put saw Macey throw 15.41m close to his personal best of 15.50m, but the Briton could only watch in amazement as Dvorak threw 16.57m to put himself in a fantastic position.