Around 20 of the world's top dancers - and both Carlos Acosta and Tamara Rojo were also taking a class there, showing that however great you are you still have to practice - spent an hour and a half working their bodies under instruction.
Total. Focus. Concentration. Control.
Yes, the dancers are used to the steps but not necessarily the sequencing relentlessly demanded by their teacher, so they really focus. I saw them watching her closely, their eyes following every tiny movement, counting the beats, making minimal gestures with their hands as they mentally rehearsed what their bodies would in a moment be required to do with precision and grace and energy.
And Loipa Araujo was focused too, not missing a beat, gently elevating a rib cage here, relaxing a shoulder there, realigning an arm, and repeating and repeating until the movement becomes second nature. With bodies like these you can't take risks, and the dancers know that their craft lies in the sort of dedication that has them practicing day after day after day.
Speaking to Fernando later - at just 25, he has been with the Royal Ballet for five years and his personal saga is a story in itself - he confirms that concentration is key.
"For those 90 minutes I focus 100%, and I am constantly monitoring my body, perfecting or extending some subtlety of movement, following my teacher's instructions."
Watching the class in action - a beautiful privilege in itself - was also like watching a masterclass in concentration. It is what keeps those dancers at the top of their game and, literally, on their toes.