Alvaro Siza made the laudable decision to devote his Royal Academy lecture last week to a single building, the church of Santa Maria-Marco de Canaveses, near Porto, Portugal.
But, ultimately, he revealed relatively little about the full complexity of what he described as a difficult project, and indeed the images he showed were all carefully controlled architectural setpieces.
At the heart of the project was the need to respond to the liturgical changes introduced by Vatican II - notably the decree that the priest must thenceforth face his congregation, rather than away from it (representing direct communication with God).
But the whole process was fraught with hesitation and doubt as to exactly how adaptations to the new liturgy were to be made, involving extensive conversations between theologians, of which we gathered mere snippets.
This created an inherent 'instability of the programme', which was clearly challenging to the architect. But it allowed the architect to 'feel useful, which is not so usual', and therefore a gratifying project to work on.
The most concrete implication of the liturgical changes identified by Siza was the implicit redundancy of the apse: an important element of the plan throughout the history of the Catholic church, and one in which a great deal of detail was traditionally invested. Siza said that 'as a functionalist architect' he was painfully aware that the apse no longer made any sense.
The response which emerged - a subtle play of convex volumes behind the altar - was in essence a pursuit of verticality within the overall formal organisation of the church, but it also 'pushes the priest towards the audience', in opposition to the traditional concave apse.
In other respects, however, the plan of the church is surprisingly conventional - a rectangular layout with rows of seating facing the altar.This would not have satisfied the more radical church designers of previous decades, who wholeheartedly embraced 'planning in the round'.
Its impact comes less from its organisation than from its formal concerns, reading as a vast volume of huge white planes interrupted only by the violent slashes of a 10m high entrance door, and a horizontal window slicing the length of one side wall at eye level to open up the interior to a view of the town and community beyond.
Siza evokes the 'wonderful atmosphere of Aalto churches', and his own memories of what a church should be like from childhood, as the primary sources of inspiration for this building; but he admits that when he visited the site he was 'in panic'.
On this 'half-ruined landscape' he seems to have succeeded in building a powerful new monument to the social role of the Catholic church in Portugal.
Alvaro Siza was delivering the Royal Academy's Annual Architecture Lecture