Wednesday, 1 August 2012:

It took a rare silver to equal the record, so it was fitting a customary gold made Michael Phelps the greatest Olympian in history.

Phelps' 15th swimming gold on Tuesday gave him 19 medals in all and took him past Soviet gymnast Larisa Latynina as the winner of more Olympic medals than anyone before him.

He'd already won more gold medals than anyone five gold medals ago, so Tuesday night's prizes cemented him as the greatest on any measure.

The 27-year-old American won six golds and two bronze in Athens in 2004 and a remarkable eight gold in Beijing four years later.

By his standards, he's had a poor Olympics in London where he arrived last week needing three medals to pass Latynina.

He missed a medal in the 400m individual medley, got to within one of Latynina with silver in the 4x100m freestyle relay and drew level with her when he was beaten into silver on the last stroke of Tuesday's 200m butterfly by South African Chad le Clos.

An hour later, there was no doubting the record would be broken with gold as he anchored home the US 4x200m freestyle relay team to an overwhelming win.

"I've put my mind to doing something that nobody had ever done before," Phelps said. "This has been an amazing ride."

It wasn't the toughest of his 15 golds, diving in with a massive lead set up by his relay teammates Ryan Lochte, Conor Dwyer and Ricky Berens.

"I thanked those guys for helping me get to this moment," Phelps said.

"I told those guys I wanted a big lead. I was like, 'You better give me a big lead going into the last lap,' and they gave it to me. I just wanted to hold on. I thanked them for being able to allow me to have this moment."

Phelps has three more events in London before retiring with a record which may be untouchable.

"It has been a pretty amazing career," he said.

"But we still have a couple races to go."

While Latynina's record lasted nearly 50 years and Phelps' will be tough to beat, China's 16-year-old Ye Shiwen showed she has plenty of medals in her after winning her second gold of the Games on Tuesday.

Ye, who's been the subject of unfounded speculation about drug use after her phenomenal performances in London, added the 200m individual medley title on Tuesday to the 400m individual medley crown she won earlier this week.

Phelps may be Olympic royalty, but real regal blood stood on the dais on Tuesday when the queen's granddaughter Zara Phillips won silver for Great Britain in the team's equestrian teams event, which was won by Germany.

Germany's Michael Jung took the double when he won the individual gold to become the first rider to hold the European, world and Olympic titles at the same time.

China continues to lead the medals table, winning three gold on Tuesday to finish day four with 12 gold and 22 in all, while the US has nine gold in a total of 23.

Britain is yet to win a gold medal at its home Games and is 24th with two silvers and two bronze.

China won its third diving gold in as many events when world champions Chen Ruolin and Wang Hao won the women's 10m synchronised platform final.

China's development in all sports continues to expand, with its first fencing gold medal when Lei Sheng beat Egypt's Alaaeldin Abouelkassem in the men's Olympic foil fencing.

The US won the women's team gymnastics final for the first time since 1996, with Russia taking silver and Romania bronze.

AAP