[1][4][11] Although the firm had little experience in ecclesiastical architecture,[4] Ronald Weeks had contributed a design to the competition for Liverpool Metropolitan Cathedral, and had worked on a new Catholic church in Machynlleth.

The design brief was for a 1,000-seat church, with the congregation grouped closely around the High Altar so that they should feel and be a part of the celebration of the Mass, in a building that would last 300 years.

The volume of the church expands from an intimate height to a soaring hexagonal spire over the High Altar, and the amount of daylight increases in proportion to the liturgical significance of the space.

[16] The concept was that on entering the cathedral at the Baptistery the people would be reminded of their own baptism (and entry into the Church), and from their places in the Nave participate fully in the celebration of the liturgy at a maximum of 15 metres [45 feet] from the High Altar with no pillars or columns intervening.

[4][16] Every effort was to be made to ensure that the interior should be free from distraction in order to help the worshippers to focus their attention on the Gospel being proclaimed and the service of worship in the liturgy, with no windows in the sight-line of the nave.

[4] Concrete is often used for its raw and unpretentious honesty, revealing the basic nature of its construction, by showing the texture of the wooden planks used for the in-situ casting forms.

[16] Another key aspect of Brutalism is that the form of the building should be driven by its intended function, and fundamentally, the cathedral design at Clifton is inspired by the analysis of the practical liturgical requirements arising out of the decisions made about the Sacred Liturgy by the bishops assembled in Rome for the Second Council of the Vatican.

[4] Parish Priest Monsignor Thomas Hughes, Fr Peter Harrison & Ken Murray carried out the traditional 'topping out' ceremony in the Spring of 1973.

[4] The vertical walls of the lower part of the building are clad with red Aberdeen Granite composite panels (made by Marble Mosaic Ltd[20]),[1] with roofing in lead.

This engraving makes a reference to the architects [Percy Thomas Partnership] and to the proportions of the equilateral triangle (and therefore regular hexagon) used by Ronald Weeks, which provide a deep symmetry in the design.

[4] The three original ceremonial doors (sponsored by Bristol City Council) were made of plywood pivoting on a central point, rendered with an artistic fibreglass by the artist William Mitchell, and bearing the Coat of Arms of the City and County of Bristol on one side and the arms of the Bishop of Clifton Dr Joseph Rudderham on the other side.

[8][4] The window closest to the Portal of St Paul is titled 'Jubilation', intended to express the Catholic concept of joy in God's Creation, and prompted by the Second Vatican Council's instructions on a duty of care for the environment.

[4] The altar [A on Plan], designed by Ronald Weeks,[4] is made of Portland stone, raised on legs (visible from the side) and contains relics of Pope Pius X (1835–1914) and Oliver Plunkett (1625–1681).

[4] Rather than a throne, here, it is a simple chair in a tall ash-wood surround bearing the coat of arms of Joseph Rudderham, seventh bishop of Clifton.

[4] Located through a tall archway from the sanctuary is the Blessed Sacrament Chapel [see Plan] a place of quiet prayer, as well as smaller or more intimate services.

[4] Its location in the Blessed Sacrament Chapel reflects the view of the Second Vatican Council that the tabernacle should be separate from the high altar, in a place of prominence and accessible to the congregation.

[4] The presence of the Eucharist is marked by a lit sanctuary lamp [E on Plan], designed by Ronald Weeks and executed in stainless steel.

[4] Brother Patrick, one of the monks of Prinknash Abbey in Gloucestershire, designed and made the steel railings bordering the space of the chapel.

[4] Whilst being primarily designed to allow free movement around the periphery of the cathedral, the columned ambulatory is also home to the fourteen Stations of the Cross [S on Plan].

[33] Originally intended to be executed in stone (it was thought that these would be damaged by later building work),[4] the Stations were made by William Mitchell using Faircrete (a mixture of concrete, resin and nylon fibres).

[4][34] It is similar to the British Museum's Lampedusa Cross[35] and is intended to reflect Pope Francis's 2017 'Share the Journey' exhortation for the Church to care for, and show solidarity to, all migrants and asylum seekers.

[4][36] The 2015–2018 £3.1 million grant-funded renovation project[4] (part-funded by £1.4m of grants from the World War I Centenary Cathedral Repairs Fund)[37][38] was carried out by Bristol-based Purcell.

[43] It has featured artists such as The Erebus Ensemble; Tom Williams (assistant director of Music at St Martin-in-the-Fields in London); The Tallis Scholars and the FIGO chamber group.

[58][20] The judges praised the interior as: 'A masterpiece of design – only to be achieved in concrete – with form and material and good acoustics creating an atmosphere which most would find totally satisfying.

[59] Martin Powell, chief executive of The Concrete Society, said: 'Clifton Cathedral has a pleasing external appearance with little evidence of weathering or deterioration.

Internally, the appearance is striking with excellent use of natural light on exposed concrete finishes, such as board mark and other patterned forms creating relief pictures.

'[1] 'The Percy Thomas Partnership produced a powerful and dramatic building, which is perhaps the most important work of one of Britain's largest post-war architectural practices'[1]

'From the 1970s, one [church] building, Clifton Cathedral, is Grade II* (Listed)'[2]Dr Robert Proctor says: 'Clifton Cathedral has recently been accused of being a 'relativist' and people-centred space, but the experience of the building rebuffs such charges as unfounded – its nave is focused on the sanctuary, and subsidiary spaces fixed in liturgically and symbolically appropriate places; ritual movement is woven into its architectural fabric; light and height give glimpses of transcendence and a clear sense of hierarchy.

Among Bristol's most exciting buildings of any style or vintage is the Roman Catholic Cathedral of Saints Peter and Paul in Clifton by Percy Thomas & Son.

The thrusting spaceship-like spire can be seen for miles around and the more-or-less hexagonal church was apparently unpopular with conservation minded locals and worshippers when it arrived from its home planet in 1974.