Scores of early-morning swimmers plunged into the North Sea at West Runton today at the start of East Anglia's first full-distance ironman triathlon.

Super-fit athletes are now tackling an 112-mile cycle circuit around north Norfolk in the middle stage of the gruelling event which will finish with a 26.2 mile run around Cromer and Overstrand.

With heavy rain and thunderstorms forecast for later this afternoon and evening, competitors look set to face some challenging conditions as the day wears on.

But the 7am swim began in perfect calm and saw 86 competitors swim 2.4 miles around the coast to Cromer where 42 individuals, including three women, peeled off their wetsuits and headed straight up the cliff to mount their cycles. Seven relay teams are also taking part. The rest were taking part in the swim only.

The first ironman competitor to complete the swim was Rob Lines, 45, of the Tri-Anglia triathlon club, in a time of 39 mins, 23 secs.

Overall swim winner was Oliver Milk, from Wymondham, in 35:25. He was competing only in the swim, as was teenager Ellie Bushell, from the University of Essex-based Human Performance Unit, who finished second in a time of 36:01.

Swim manager Jim Keeble said everything had gone 'brilliantly' and all those who entered the water had completed the swim, helped by a tide which pushed them in the right direction. Competitors had ranged in age from teenagers to those in their 60s.

Cromer and Sheringham inshore lifeboats joined 12 paddle-boarders to keep an eye on the swimmers while coastguards and lifeguards watched from land.

Mr Keeble thanked RNLI manager Vincent Pank for organising the water safety aspects of the race.

He said the place and timing had been carefully chosen to make the event as safe as possible and avoid any of the problems faced in May's Southwold Pier to Pub Swim when swimmers got caught in a strong tide and 85 had to be rescued by RNLI lifeboatmen and lifeguards.

Among this morning's swim-only competitors was Marcus Nichols, 37, from St Cross, South Elmham, near Harleston, who was trying an ironman swim for the first time.

'It was absolutely superb - by far the best sea swim I've done. I was amazed at how crystal-clear the water was. It was lovely and warm - I would have liked to have stopped and done a bit of crabbing!' said Mr Nichols, a graphic designer, who has been competing in triathlons for the past two years but has not yet tackled the full ironman event.

He set his alarm for 3.45am this morning, ate a Nutella sandwich and collected fellow Bungay Black Dog Running Club member Tom Pullinger, 42, from his home in The Street, Pulham St Mary, en route for West Runton.

Mr Nichols completed the swim in 43:50 and Mr Pullinger in 42:25.