The objective was to raise about $600,000 (£500,000) to buy Personal Protective Equipment (PPE) for health workers and and vulnerable veterans in Commonwealth countries.
Mr Hammond said he was inspired by Capt Sir Tom Moore, a British veteran, who raised more than $35m for the UK's National Health Service.
Prince Harry said that Private Hammond and Capt Tom More - who celebrated his 100th birthday during his campaign - had set an example to the world.
Private Hammond, who met Prince Harry last year at the Field of Remembrance in London, said he was grateful for the letter.
He was drafted into the Royal West African Frontier Force aged 16 to fight in WWII.
Although he finished the seven-day walking challenge in May, the fundraising campaign continues. He has so far raised $28,000. Read Full Story

Facebook
Twitter
Pinterest
Instagram
Google+
YouTube
LinkedIn
RSS