Professor Stephen Hawking's revealed how he has always tried to 'lead as full a life as possible,' in response to a plea for inspiring message.
Other A-list stars, including actor Sir Ian McKellen, athlete Jessica Ennis-Hill, actor Sir David Jason and sailor Dame Ellen MacArthur also shared some words of wisdom.
The first to arrive was from the 73-year-old scientists and author, who suffers from motor neuron disease.
Professor Hawking wrote: 'I have always tried to overcome the limitations of my condition and lead as full a life as possible. I have travelled the world, from the Antarctic to zero gravity.'
He accompanied his message with a thumb print.
Mr Rhodes, 46, from Southampton, Hampshire, fired off 25 letters to some of the most famous names in the country and in total 18 replied.
In return, he made a £100 donation to a charity of the celebrity respondents choosing.
Mr Rhodes, who is the managing partner at law firm Trethowans, said: 'I was pleasantly surprised that so many came back and it's the little bits where they have gone over and above.
'But the one where I sat down and held it because I didn't expect to get it was Stephen Hawking. It made me smile the most.
Mr Rhodes came up with the idea last year to motivate the 150-strong staff but wanted to use words that were not 'corporate speak'.
He said: 'We all look at these motivational messages like 'sell more' and 'buy more' but they can have the opposite effect.
'I wanted something that would motivate and the only way I thought I could do that was not by having our words.
'So I dug out the quotes and wrote to them all saying I was trying to motivate the next generation of our staff.
'I told them I have read what they have said and how I thought it was motivational and said that if they were able to send a signed photograph with a message to our staff at Trethowans I will give £100 to their favorite charity.'
The quotes and photographs of each of the celebrities have now been split between their new office in Southampton and a second office in Salisbury, where they have been hung on the walls of the staff seating area.
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