Mark Lewis has asked Guinness World Records to recognise his longstanding project The Strand as the world's only ever-changing mural.
Mapping the city in stylised form, the mural is on the 3,000 sq ft wall of a building at the junction of Waverley Road and Clarendon Road in Southsea.
Muralist Mark, 52, first painted the mural in 1997 before it was damaged by a leaking pipe and redone in 2010.
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Around 150 people have been involved in the project in the last 23 years.
Recent additions include the Salvation Army Brass Band, private houses, and touching memorials that people have paid to add
On the prospect of winning a record, Mark said: ‘It would be humbling – it would finally recognise that mural for what I intended it to be, and that's an outstanding community project.’
He said the mural has never suffered from vandalism as it unites the differing communities in an area lived in by the rich and poor.
‘Everyone is shocked it’s never been vandalised – it’s so loved round there,’ he said.
‘Everyone knows a story about it.
‘It’s a real diverse area but there’s one thing that unites everyone in that area and it's that mural.
‘Everytime I go down there I have to spend twice as long there as I spend half the time talking and half the time painting.’
Dad Mark hopes his 15-year-old daughter Jesma Lewis, who is studying art, will take on the mantle to continue the mural as he has a 99-year lease on it.
More shops and restaurants have recently been added, including Sakura restaurant in Albert Road and the One Legged Jockey vintage store in Marmion Road, both in Southsea.
Eunice Woods, 82, asked Mark to paint her husband George Woods, 83, onto the mural two months ago after he died three years ago.
She also asked Mark to paint the Salvation Army band her husband performed in, and for whom she was in the choir.
Her family were delighted with the tribute.
‘It’s a good depiction of Portsmouth, hopefully it will stay there for a long time,’ she said of the mural.
A previous study showed trade at firms near the mural was boosted by 30 per cent when it was made, Mark said.
Mark, the former operator of the Arts Lodge in Victoria Park, equates this to £1m in income over the years, compared to his £10,000 income from it in a year.