"Lovely to be joined by HRH Prince Harry and Meghan Markle this morning at the Anzac service in Hyde Park," Adams tweeted.
Prince Harry and Markle were welcomed by the London Maori club with a hongi and laid a wreath near Wellington Arch.
According to British media, the wreath included a handwritten note from Harry, which read: "For all those who have made the ultimate sacrifice in pursuit of our freedom. Thank you. Harry".
Foreign Minister Winston Peters attended an Anzac service in Singapore.
He was hosted by in Singapore by Minister of Defence Dr Ng Eng Hen, with whom he discussed international and regional security issues over lunch.
They were expected to discuss the coalition Government's ban on foreign purchases of property – which could have implications on New Zealand's free trade deal with Singapore.
During his previous stop in the UK, Peters was photographed enjoying some cricket with Nigel Farage, the former head of the UK Independence Party and the key architect of Brexit.
Farage posted a picture of the pair on Twitter with New Zealand and English flags today, saying: "We need closer ties with our Commonwealth friends".
Despite being a prime architect of Brexit leading up to the 2016 vote, Farage has recently made public his view a second referendum for Brexit could make sense.
As an Opposition MP, Peters has previously spoken at a Commons meeting arranged by Farage.
Before she returned to New Zealand earlier this week, Prime Minister Jacinda Ardern also took the opportunity to meet with political allies, stopping in on Labour leader Jeremy Corbyn and MP Emily Thornberry.
It was a private visit and not part of Ardern's official itinerary.