The event began with words from the chairman of trustees Khalid Aziz, who introduced the Lord Lieutenant.
After unveiling the plaque, the Lord Lieutenant and guests were shown around the small brewery, tasted samples of the beers and were each given a presentation pack of beer specially brewed to mark the occasion.
The Lord-Lieutenant said: "The four beers I have tried from Gilbert White’s Brewery were very good indeed. There was one in particular I was particularly pleased with, and I am sure you will do exceptionally well."
The brewery is based in Gilbert White’s original brewhouse, built by White in 1765, and re-opened for production in 2019.
Re-equipping the brewery was supported by grants from the European Agricultural Fund for Rural Development, South Downs National Park Sustainable Communities Fund, East Hampshire District Council and 15 founder members who contributed at least £250.
The brewery is run by volunteer brewers headed by Gren Earney, John Elder and Andrew Murphy.
Apart from being a keen naturalist, Gilbert White was also an avid brewer who kept a regular diary of his brewing exploits over the decades. He was even in his brewhouse bottling up beer 13 days before his death in 1793.
The Gilbert White Brewery beers are available from the museum’s gift shop and cafe, and can also be found on tap at The Selborne Arms.
The brewers also make seasonal brews, which can be tasted at the forthcoming Gilbert White Christmas Fair on Saturday, December 4.