Humphrey's father Thomas Weld (of Lulworth) donated the land and endowed the Jesuit college at Stonyhurst.

In 1848, Weld declined an offer by the Governor of New Zealand, Sir George Grey, of a seat on a proposed nominee council.

In 1852 he visited England, where he published a pamphlet, Hints to Intending Sheep Farmers in New Zealand, which ran into three editions.

He became a member of the 1st Parliament as the representative of Wairau, an electorate in the northeast of the South Island; he was declared elected unopposed.

Acting Governor Robert Wynyard managed to block this move, however, and Weld's role as a "minister" came to an end.

[1] In 1860, Weld was invited to join Edward Stafford's government, taking over responsibility for Native Affairs from William Richmond.

Weld, believing that it was British ineptitude that caused conflict with the Māori in the first place, strongly objected to Grey's demands that Parliament should fund the troops.

Weld instead believed that British troops should be removed from New Zealand altogether, and be replaced by local forces.

Weld's other success, the withdrawal of British troops from New Zealand, was also controversial, and generated considerable hostility from the Governor.

He immediately embarked on a series of tours of the state, which saw him travel about 1,200 miles (1,900 km) on horseback in his first six months in office.

Weld saw his appointment to the governorship as a mandate to institute similar constitutional changes to that achieved in New Zealand.

Although Weld did not think that Western Australia was ready for responsible government, he accepted the situation and passed on the request to the Colonial Office in London.

The Colonial Office were strongly against granting responsible government, and were critical of Weld for allowing the situation to arise.

He found the role much less taxing than in Western Australia, as Tasmania already had responsible government and his main duty was to preside at meetings of the Executive Council.

Louch (1966) writes of Weld's seven years in Singapore: "It was there with his wealth of experience that he found the fullest scope for his talents as a colonial administrator, and where he is best remembered now."

the town of Taiping has been much improved since the fire, which took place rather more than a year ago; new streets have been laid out to considerable width, and a better class of houses has been built" The construction of the Taiping – Port Weld railway was the beginning of a major transformation altering radically the landscape of the Malay Peninsula.

He also put into effect plans to build a telegraph line along the road linking Taiping with Province Wellesley.