I would research this problem a little. Depending on where you live, it may be common to have moist soil for long periods of time. Camellias love evenly moist soil as this is what their environment is like in the southeast of the US, Asia (tropics all the way to Japan) and some areas in Europe. Their roots are typically found in the top 10 cms of the soil so, if you insert a finger into the soil to a depth of 10 cms and the soil feels dry or almost dry, you can water them. But if the soil feels moist or soggy, do not water yet (keep checking the soil though).
However, if the soil is soggy for long periods of time, you may need to figure out why, especially if the soil is not soggy in other nearby places that are similar to this internal yard. The lack of sun and wind makes it more difficult for the water to evaporate. The type of soil - high clay content or soils with a shallow depth to bedrock- may help cause this.
The good news is that, for moist soils, this simply allows for more time in between waterings but, there is a difference between moist and soggy. If you think the soil is soggy, I would also investigate to make sure there is not a water leak from water pipes that are causing the soil to be soggy. An unscientific test for soggy soil may go like this... insert two fingers in the soil to a depth of 20 cm and extract some soil; press the soil with both fingers and observe if you see water droplets forming. If you observe water droplets, it may be too soggy. Since it is an internal yard, water may have difficulty evaporating and exiting.
Some people here with this problem will contact a landscape company to install a French drain that leads excess water out somewhere. If you contact a landscape company, they may dig a 30 cm wide by a 30 cm deep hole, fill it with water and let it sit to observe how long it takes for water to percolate down. Then they will suggest options. They may also check any automated watering systems in this internal yard.
If you cannot resolve the problem and are concerned for the camellias, consider growing the camellias in containers so the roots do not develop root rot. Or switch to more water-tolerant plants. Anaerobic soils (soil that lack much oxygen due to too much water) can develop bacteria and may be smelly.