The pair remain a class above the rest of the field, with the United States' Kendell Williams in third, 187 points behind Thiam.

And Johnson-Thompson will allow herself to dream of victory overnight.

She said: "Why not? It's something that I'm aiming to do. It's something I'm in shape to do and I'm in a very good position to do it.

"But you never know with these things on day two. I've worked very hard on my day two so we'll see what happens.

"I know I'm in good shape and I can contend. I don't think 'I need to be in the lead by this many points'.

"Apart from the 200m it was a great day. It's just the halfway point, another day to negotiate tomorrow but I'm in a good position."

Johnson-Thompson, who came second to Thiam at last year's European Championships, excelled ahead of Thursday's long jump, javelin and 800m.

She posted two personal bests in the 100m hurdles and shot put.

The World Indoor pentathlon champion made the perfect start to kick-start her bid for gold with a huge lifetime best of 13.09 seconds in the 100m hurdles.

Johnson-Thompson appeared shocked by the time after winning her heat.

Her and Belgium's Thiam then went blow for blow in the high jump, with both finishing with clearances of 1.95m.

In the shot put, one of Johnson-Thompson's weaker events, she shone again to throw a personal best of 13.86m, to come second behind Thiam, who registered 15.22m.

In the 200m she clocked 23.08secs, a season's best, to win heat three.

Johnson-Thompson added: "That's a great day. It's a season's best in 200m, but obviously it isn't where it was in the last couple of years.

"It's obviously something I need to work on next year. There were PBs in other events so I'm over the moon."