The British team also held the lead after good efforts from their first two riders - Jeanette Brakewell, now lying sixth on Over to You, and Kristina Gifford, who is in eighth place on The Gangster II.
The two British women looked relaxed and confident, despite the urgency of their quest to retain the European title and, even more important, to qualify for next year's Olympic Games in Sydney.
Powell and Flintstone IV were, however, in a different class in the dressage arena yesterday. The horse, who looked relaxed and fluent, showed more impulsion than any of the other horses here.
Flintstone had almost two years off following a tendon injury in the spring of 1997 - a fact which had to be taken into consideration when the selectors debated on whether or not Powell should be one of the four team members.
The rider has no complaints about their decision to give him an individual place - "I'm still riding for Great Britain as part of a squad of six," he said.
Brakewell, who will be second of 78 riders to tackle the cross-country course tomorrow, felt that Over to You had produced one of his best ever dressage tests.
She can now concentrate on the cross-country fences, notably the first water complex (fences four to seven). "It's a big question to ask so early on the course, it might be the long route for me," she said.
Gifford, who won team gold medals at the 1994 World Games and the 1995 European Championships, has one of the least experienced horses in The Gangster II, a giant of 17.2 hands who made every effort to please her yesterday.
"He's a lovely horse to ride, very kind and willing," she said of the nine-year-old, with whom she finished fourth at the four-star event in Kentucky in April.
The last two British team members - Pippa Funnell on Supreme Rock and Ian Stark on Jaybee - will be riding their dressage tests today. All four will then carry a burden of expectation in tomorrow's cross-country, which will be the crucial test for those still seeking Olympic qualification.
Until the 1996 Olympics in Atlanta, when quotas were introduced for the first time, any country could enter for the Games as long as their riders could comply with the eligibility requirements.
With nine European nations seeking qualification through one of the three places on offer here, there is far greater pressure than ever before. The Belgians and Germans are (like Britain) on an urgent mission to gain tickets for Sydney here.
"We have the strongest team we have ever had," Belgium's Constantin van Rijckevorsel, now lying second on Otis, said yesterday. However, since finishing eighth individually in the Atlanta Olympics, Otis has taken a few tumbles.
The horse fell at Bramham and at the World Games in Italy (both on treacherously sodden ground) last year. This spring he stumbled over a tree trunk at Saumur, before completing a safe and steady clear round at Punchestown.
His 23-year-old Belgian rider, who is one point ahead of the Swedish airline pilot Paula Torquist, nevertheless seems full of confidence as he prepares for the cross- country. Tornquist, who has competed in gymnastics and free style skiing at top level, only began riding in 1990 at the age of 26. She has since won a team silver medal at the 1997 European Championships and individual bronze at last year's World Games with her game Irish bred gelding SAS Monaghan.
EUROPEAN THREE-DAY EVENT CHAMPIONSHIPS (Luhmuhlen, Germany): After first day of dressage: 1 Flintstone IV (R Powell, GB) 72 penalties; 2 Otis II (C van Rijckevorsel, Bel) 82; 3 SAS Monaghan (P Tornquist, Swe) 83; 4 Sir Toby IV (M Loheit, Ger) and Land Rover Discovery (N Haagensen, Den) 84; 6 Over to You (J Brakewell, GB) 87. Other GB: 9 The Gangster II (K Gifford, GB) 89; 22 Cornish Envoy ( K Parker) 106. Teams (after first two riders): 1 Great Britain 176 penalties; 2 Belgium 183; 3 Sweden 186; 4 Italy 198; 5 Germany and Portugal 204.