Britain's Royal Weddings is an elegant and detailed documentary that encapsulates the glamour, anticipation, and tradition attached to the prestigious and globally celebrated royal weddings in the United Kingdom. This two-part historical film, taking centerstage in the realm of documentaries, focuses on the extravagant and historic royal nuptials from 1923 onwards.

The documentary delves deep into the intricate details of the royal wedding ceremonies right from the engagement customarily announced to the world, the bride's iconic wedding dress, the elaborate festival-like arrangements, the grandiosity of the cathedral, till the newlyweds’ first appearance as a wedded couple. Moreover, these weddings are not just about extravagant ceremonies and regality. They also serve as a mirror, reflecting the changes in society over time, highlighting evolving traditions and norms.

The journey begins in 1923 with the wedding of Queen Elizabeth II's parents, the late King George VI and Queen Elizabeth, known fondly as the Queen Mother. This section of the documentary not only discusses the grand event but also explores the profound emotional impact it had on the British public in the aftermath of World War I. The public wedding, a departure from the private ceremonies of the past, marked an unprecedented move that arguably restored widespread optimism and hope in a beleaguered nation.

The trajectory of royal weddings as the centerpiece of global interest continues with the nuptials of Queen Elizabeth II and Prince Philip in 1947. A nation striving to recover from the ravages of World War II saw in their wedding a beacon of hope and joy. The film incorporates never-seen-before archive footage and enchanting anecdotes from people who participated in these ceremonies, thereby giving viewers an intimate peek into these very private, yet globally followed occasions.

The late 20th-century royal weddings, notably that of Prince Charles and Lady Diana Spencer in 1981, become another high point of this documentary film. An event watched by millions around the world, their wedding was seen as a contemporary fairy tale moment. The documentary showcases the fine details of this spectacle – the mesmerizing wedding gown, the carriage ride, the young, vivacious bride – capturing the euphoria of the time. Although the film recounts the joyousness of these occasions, it avoids falling into the trap of retrospective judgement, leaving viewers to reflect on the public personas and private individuals behind the spectacle.

The film also takes a look into the fresh perspective of royal weddings which emerged with the 21st century, marking a distinct departure from the past. The wedding of Prince William and Kate Middleton in 2011, and Prince Harry and Meghan Markle in 2018, not only echoed the grandeur of their predecessors but also embodied a more modern and accessible interpretation. Emphasizing the shift in societal norms and public expectation from the monarchy, these weddings signaled the dawn of a new era.

Besides touching on all major royal weddings, the documentary also intelligently weaves in the stories of the lesser-known royal weddings, thereby painting a comprehensive picture of traditions, sentiments, and public perceptions attached to these events.

"Briatin's Royal Weddings" is not just a film about opulent wedding ceremonies, magnificent bridal gowns, and royal glamour. It is a reflection of history, societal change, aspirations, and evolving norms and values throughout the 20th and 21st centuries. It lucidly portrays how these royal weddings were not only personal moments of joy for the royal family members but also significant historical moments that were deeply ingrained in the national psyche and world history.

Backed with outstanding visuals, cinematic storytelling, and meticulous research, Britain's Royal Weddings makes for an enchanting watch that transcends the barrier of being a mere historical documentary. It offers vivid insights into the fascinating world of royal weddings, and stipulates unforgettable fascination for royal-watchers, history enthusiasts, and romantic minds alike, thereby making it a must-watch cultural feast.