Where in London, even in the middle of one of the city’s busiest summers, will you be able to get a fantastic view across the rooftops, while not having to queue for very long if at all? The answer certainly isn’t the London Eye, which is likely to be mobbed with tourists through the Olympic weeks ahead. No: it’s Westminster Cathedral, whose bell tower is one of the easiest, and most accessible ways to get a bird’s eye view of London (and there’s even a lift).

And as you gaze out across a wonderful city from a height of 200 feet, it’s interesting to muse on the fact that, whether or not the streets of London are paved with gold, they’re certainly paved with Catholic history – and much of it remains largely hidden, a long-term legacy of the Reformation and the long struggle that followed.

Westminster Abbey is the nation's church and every monarch has been crowned there since 1066. It literally groans with history and until the middle of the 16th century, its history is entirely Catholic.

As a result, Catholic London divides quite sharply into two periods: pre and post-Reformation. The traces of the early period are there in plenty, but they’re often now housed in Anglican churches and cathedrals. Westminster Abbey is the most obvious example of this: it was originally a Benedictine monastery, and then rebuilt by Edward the Confessor (whose burial place and shrine it is) and then again in the 13th century, in Gothic style, by King Henry III. Westminster Abbey is the nation’s church, and every monarch has been crowned there since 1066. It literally groans with history – and until the middle of the 16th century, its history is entirely Catholic.

Then came the Reformation and the dissolution of the monasteries and the handing over of Catholic churches to the Church of England – so the history of Roman Catholicism over the next few centuries is a hidden history, although all the more fascinating for that. During the years of persecution the wealthier Catholics usually attended Mass in the chapels of the embassies of Catholic countries such as Spain – where Masses could not be made illegal – and the more ordinary folk were often alerted to underground celebrations of the eucharist held in taverns (see box). The history of this period is a bloody and violent history of persecution, with Catholic priests and worshippers often condemned to die in desperately unpleasant circumstances. The Tower of London – where, amongst others, St Thomas More was held before his execution – is one of the best places in the city to get a feel for the history of that period, and messages written by some of those who were held there can still be seen etched onto its walls.

For an even greater insight into the suffering of those times, though, the best place to head is Tyburn Convent, which is tucked away a stone’s throw from Marble Arch. For hundreds of years, including the period of Catholic persecution, a site called ‘the tree’ was nearby. This was the gallows; and an especially horrific gallows it was too. Between the 12th century and 1783 thousands of people met their end here, including the Catholic Tyburn martyrs who are especially remembered by the sisters of Tyburn Convent, a community of the Adorers of the Sacred Heart of Jesus of Montmartre. Their vocation lives out a prophesy made during the trial of a 16th century Catholic priest, Father Gregory Gunne, who told his accusers that 'the day will come when you will see a religious house built there (he gestured towards the gallows) for an offering'.

And as well as offering prayers daily for the martyrs who died at the nearby gallows, the convent houses an extraordinarily moving collection of relics. There are pieces of bone, hair and fingernails; some come from elderly people, some almost into their nineties, who were dragged to their deaths for being Catholics. Three times a day, at 10.30am, 3.30pm and 5.30pm, a sister leads a tour of the convent’s collection of grisly, but remarkably thought-provoking, treasures.

While it’s true that most sites of Catholic interest in London are either definitely pre, or definitely post, Reformation, there is one church that straddles both histories. It’s St Etheldreda’s, and it’s the oldest Catholic church in use in the city. It was the former London home of the Bishops of Ely, and it fell into disuse after the Reformation – only to be bought back by the Catholic Fathers of the Institute of Charity for £5,400 in 1873. Among the statues inside are ones to early Christian saints including the eponymous St Etheldreda, as well as St John Houghton who was executed at Tyburn in 1535. During the persecution years, the crypt of St Etheldreda’s was often used to house Catholics in need of shelter.

For and even greater insight into the suffering of those times,the best place to head is Tyburn Convent

Several great churches across London bear witness to the years since the persecution times: as well as Westminster Cathedral, there’s the beautiful Jesuit Church of the Immaculate Conception in Farm Street, Corpus Christi on Maiden Lane which was opened in 1874 by Cardinal Manning and hosts many thespian events, since it is in the centre of theatreland, and the London Oratory, often incorrectly called Brompton Oratory, which was founded in 1849 after Blessed John Henry Newman had founded the Birmingham Oratory (until the opening of Westminster Cathedral in 1903, this was the country’s mother church).

Less famous than these, but equally fascinating and recently reopened after major restoration, is St Patrick’s in Soho Square, which was opened in its present building in 1893 (previously, the church operated out of a nearby ballroom). St Patrick’s was set up after Catholic worship was legalised, to support the large, impoverished Irish community that lived in that area. Through the years since it has had many famous entertainers associated with it: Danny la Rue was one of its altar servers, and Tommy Steele was married here in 1960. And the American Archbishop Fulton Sheen, the first-ever Catholic TV evangelist, always celebrated Mass here when in London, and often preached from the church’s impressive pulpit. To this day the actor Martin Sheen – who was born Ramon Estevez, but who took the name Sheen in honour of his favourite archbishop – can often be seen in its pews whenever he’s in town.