Newshub can reveal New Zealand's representative in London, Sir Lockwood Smith, is retiring and will leave his post early next year.

His decision follows the UK announcing a clampdown on Kiwi expats, but the High Commissioner doesn't count that as part of his legacy.

New Zealand House towers above central London and for the past three years, Sir Lockwood has been King of the castle.

He says while it's up to the Government to announce the official end date, the rough term is a bit less than a year to go.

There was a chance the term would be extended another year beyond that -- the last High Commissioner's was.

But when Sir Lockwood met John Key in New Zealand recently, the extension wasn't agreed.

"I think one's got to accept there's a limit to the time one can be effective," Sir Lockwood says.

For the Prime Minister, it means freeing up the prized role.

Speaker of the House David Carter is widely tipped to get the job. He would be the third Speaker in recent memory to be posted to London, after Sir Lockwood and Jonathan Hunt.

"I'm sure he'd be a very good candidate but you know the decision is not one for me to make," Sir Lockwood says.

It's tough times for the New Zealand/United Kingdom relationship. Just before Easter, there was another crack down on New Zealanders -- a $2000 fee for skilled Kiwis to be sponsored in the UK.

And last month, a health surcharge of $440 was added to Kiwi visa applications.

"I wouldn't say it's at an all-time low, but what worries me is the direction you know, this endless chipping away of the relationship," Sir Lockwood says.

Sir Lockwood isn't taking this personally as a blight on his legacy here.

The UK was always going to do what it wanted with immigration, no matter the fight put up by New Zealand.

And from game show host, politician, minister of various things, diplomat and prized bull breeder -- Sir Lockwood says he's never one to look back.

"I'll be retiring happily to my farm in New Zealand. We love New Zealand," he says.

"It's very long hours and a very full work programme, and I'll be looking forward to a rest."

And after more than three decades in politics -- fair enough too.

Newshub.