In the centre of our Galaxy lies a supermassive black hole, identified with the radio source Sagittarius A*. This black hole has an estimated mass of around 4 million solar masses. Sagittarius A* is quite dim in terms of total radiated energy, having a luminosity that is a factor of 1010 lower than its Eddington luminosity. However, there is now compelling evidence that this source was far brighter in the past. The evidence for which, is derived from the detection of reflected X-ray emission from the giant molecular clouds in the Galactic centre region. However, the interpretation of the reflected emission spectra cannot be done correctly without detailed modelling of the reflection process. Attempts to do so can lead to an incorrect interpretation of the data. In this thesis, I will present and outline the creation of a Monte Carlo simulation code, developed in order to fully model the complex processes involved in the emerging X-ray reflection spectra. Through the use of Xspec table models, the simulated spectra can be compared to real data in order to derive model parameters and help to constrain the past activity of the black hole. In particular, the code is applied to observations of Sagittarius B2, the largest and most massive giant molecular cloud in the Galactic centre, and used to constrain several parameters of the cloud. This work confirms some values already present in the literature and sheds new light on one of the largest uncertainties in this field, the line of sight position. In turn, it provides some of the best estimates to date for the flaring luminosity of the incident source.