The club – and the Vunipola family – were due to have two representatives on the 2017 Tour to New Zealand, only for a shoulder injury to prevent Billy joining his elder sibling on Lions duty.
But the inspiration the brothers provided at their former club prior to that series against the All Blacks means they may not be the last Lions to come from the Gloucestershire outfit.
Mako, who was on his second Lions Tour in 2017, shone up front throughout and impressed head coach Warren Gatland with his performances in the domestic Tour matches.
The loosehead prop was particularly dominant against Crusaders in Christchurch, illustrating his powerful ball-carrying and being rewarded with a starting spot in all three Test matches.
It took Mako’s run of Lions Test starts to six in a row after his performances in Australia in 2013.
The England prop was handed a stiff challenge up against All Black stalwart Owen Franks in the scrum, but Mako came through it with aplomb as the Lions pack held their own at the set-piece.
His performances helped the Lions to a thrilling series draw – the first time they’d avoided a series defeat in New Zealand since 1971.
Mako and Billy will both be looking to impress over the remainder of 2020 as they seek selection for the 2021 Tour of South Africa – and those at their boyhood club will watch on proudly as the brothers continue to shine on the global stage.
The Saracens duo returned to their roots in February 2017 to coach the same junior section they had each spent three years with earlier in their own respective rugby journeys.
🔙 where it all began…@bvunipola and @Mako_Vunipola return to their former club @ThornburyRFC 🏉 pic.twitter.com/vLoolvTlyZ
— England Rugby (at 🏠) (@EnglandRugby) March 1, 2017
And club chairman Geoff Sprackman – team manager of Mako’s age-group side all those years ago – admitted it was a dream come true for the entire club.
“It was massive for the club, it inspired the kids. We had a lot of juniors there and they all walked home feeling 12ft tall that day,” said Sprackman, speaking after the event in 2017.
“It inspires everybody, they all get the feeling that they can go on and do something.
“But also it feels great to know they played at the same club as the Vunipolas – that’s a massive thing.
“The nice thing is that on the visit the boys were still exactly the same.
“They didn’t come down in all their England kit or anything like that, they didn’t show off – they blended in with everyone else and were just two really nice lads.
“They were always like that and it’s just nice to see. They have really inspired the club – it was just fantastic to have them for those three years.”
Sprackman spent a lot of time coaching the Vunipolas – particularly Mako, as he was the same age as Sprackman’s own son Ben.
And the class, both on and off the field, of the future England internationals was always clear to see before they left for school scholarships at Millfield (Mako) and Harrow (Billy).
“Because I lived nearby, I used to visit the club and watch the rugby and then when my lad Ben got started 20 odd years ago, I started to get really involved,” added Sprackman.
“Ben is the same age as Mako, he played with him for three seasons and went to school with him.
“Mako and Billy were always bigger than the rest of the guys but they also had a natural ability to play rugby.
“They were gifted and, to be honest, they did stand out from the crowd. Their ball-handling skills were fantastic.
“All the time they lived in Thornbury, I never saw them without a rugby ball in their hands.
“I didn’t have so much to do with Billy because he was two age groups below but I used to pick up Mako and drive him to games.
“It’s a funny feeling when you watch the guys playing for England. I went to Twickenham in 2017 in the Six Nations, and to see them out on the pitch was just amazing.
“You can’t believe that they were once at your club – it’s humbling and it’s lovely.”
Founded in 1963, Thornbury first XV currently ply their trade in the South West 1 West division, where they finished second in the 2019/20 season and narrowly missed out on promotion to the fifth tier of English club rugby.
Rhys Oakley was the first full international from Thornbury RFC. He played for Thornbury before joining Bristol and subsequently being capped twice for Wales in 2003.
Former Connacht and Ireland training squad centre Darren Yapp also came through at the club but there is no doubting the real heroes at Brockhampton Hill.
If they can play together in a Lions jersey in 2021, it really would put the icing on the cake for the Vunipola brothers – and everyone back at Thornbury.