A German lawyer who spent 15 years re-enacting episodes of the TV quizshow Who Wants to Be a Millionaire? in his cellar, said his hobby had paid off as he walked away with the top prize this week.

Jan Stroh, 35, even crudely reconstructed the studio of the German version of the programme in the basement of his Hamburg home, complete with palm trees and exotic seascape backdrop, victory glitter and sound effects.

After years of rejections having applied to be a candidate, he was finally invited on to the show as a reward for his loyalty for its 20th anniversary on Monday.

He told the host, Günther Jauch, he had never missed any of its 1,407 episodes, escaping family celebrations as a teenager in order to watch the show when it first launched. He had habitually pored over the questions and answers afterwards, he said, trying to learn as many as he could by heart, and invited friends over for quiz nights in which they switched between the roles of contestant and quiz master.

“The fact that I have spent almost 16 years re-enacting the show on my own quiz stage, complete with all the buzzer and bell sound effects, certainly gave me an advantage,” he told the tabloid Bild in an exclusive interview.

“Of course the excitement was huge, especially having applied so often, and then to really be sitting opposite Herr Jauch, my biggest fear was to have a blackout.”

Facebook Twitter Pinterest Stroh answers questions on the quizshow. ‘My biggest fear was to have a blackout,’ he said. Photograph: kommunikation.mediengruppe-rtl.de

He said he was able to relax after answering the €500 question. “I thought to myself: everything will be fine, just try to imagine this is a normal quiz evening at my own quiz stage.” He said trust in his own instinct and the support of friends proved to be his best aids.

Wer Wird Millionär, based on the original British format, runs twice a week and is a magnet for television audiences in Germany.

The British version first aired in 1998 and was broadcast for the last time in 2014 after audience figures waned. The format continues in 50 countries worldwide and the German version is the longest-running.

It has proved enduringly popular, despite the fragmentation of the media landscape. It attracted almost 6 million viewers on Monday night, or 22.6% of the audience share. Despite the fall in the number of young people watching TV, it attracts a 21% of 14- to 49-year-olds, according to the industry observer Meedia.

At its height a decade ago, when WWM ran three times a week, its audiences were up to 8 million. Out of 2,800 candidates, 11 – including Stroh – have gone home as millionaires. Jauch, its presenter, himself a multimillionaire, has called it “the last campfire around which several generations continue to gather together”.

Stroh said he was not planning to give up his job working as a lawyer for the city of Hamburg, but wanted to use his €1m (£910,000) to buy a new suit, go on holiday to Australia, donate money to a charity working to protect the common swift and to give his quiz cellar an extensive makeover.