Whilst clearances in 1812 went reasonably smoothly, in 1813 Sellar failed to negotiate successfully with angry resistance in the Strath of Kildonan.

His actions here gave rise to a number of charges brought by the sheriff-substitute Robert McKid, who was an enemy of Sellar.

Sellar was keen to express his opinions on the management of the Highlands, writing highly emphatic letters on the subject.

He soon became the leading solicitor of the area, building up a fine reputation and a status much advanced from his father's lowly origins.

[1]: 21 His father's business provided some degree of training for the factors on the Seafield estate, a major client of Thomas's law firm.

[1]: 19-20 The Sellar family were involved in the building of a harbour at Burghead, Thomas as an investor and Patrick carrying out legal work.

[a] As the building work finished in 1809, some of the investors travelled on the harbour's new packet service to Dunrobin Bay in Sutherland.

Young was sixteen years older than Sellar, and had an impressive practical record of agricultural improvement in Morayshire.

An up-to-date drainage scheme was installed, though some marshy areas were used to grow flax (which had not previously been grown in Sutherland).

Whilst applying their energies to demonstrating their methods, the pair offered much free advice on improvement to Lady Stafford, which she was keen to hear.

Whilst Lady Stafford was a child, her guardians had made some modest progress at improving the rental income by modernisation.

This shortage of money continued in the early years of the Staffords' marriage, however, in 1799 some clearances were carried out, together with rent increases.

After Young and Sellar's arrival in 1809 and their frequent advice to Lady Stafford, Falconer's position was being steadily undermined.

[c][1]: 36-66 After Falconer's resignation, William Young and Patrick Sellar were appointed in the position of factor, as a joint role.

However, in 1813, planned clearances in the Strath of Kildonan were accompanied by riots: an angry mob drove prospective sheep farmers out of the valley when they came to view the land, and a situation of confrontation existed for more than 6 weeks, with Sellar failing to successfully negotiate with the protesters.

Ultimately, the army was called out and the estate made concessions such as paying very favourable prices for the cattle of those being cleared.

The whole process was a severe shock to Lady Stafford and her advisers, who were, in the words of historian Eric Richards, "genuinely astonished at this response to plans which they regarded as wise and benevolent".

[d][5]: 163  These were complicated by Sellar having successfully bid, in December 1813, for the lease of one of the new sheep farms on land that it was now his responsibility, as factor, to clear.

[4]: 180  In his role as factor, he was legally precise in issuing the required notices of eviction to those being resettled, doing this in January 1814 in conjunction with rent collections.

It caused consternation among the outgoing tenants, as it deprived their cattle of food, so putting them in poor condition for their imminent sale.

A further problem was that Young was slow in organising the setting out of the new coastal lots, and in March and April, those under notice of eviction had no details on where they were to go: each needed time to build a house.

[5]: 163–164  At Young's request, Sellar made concessions to some tenants, allowing them to stay in their properties a little longer, but this just created confusion among those evicted.

The delay was a problem for Sellar: his newly purchased flock of sheep was temporarily housed at his farm at Culmaily, but were short of food due to the level of overstocking and started to die.

[4]: 181  As was normal practice, the roof timbers of cleared houses were destroyed to prevent re-occupation after the eviction party had left.

[1]: 182, 195  Robert Mackid had to leave the county to rebuild his career elsewhere, providing Sellar with a grovelling letter of apology and confession.

Sellar's plans for purchase of supplies were regarded as over-generous by the estate, so there was great hardship in many parts of Sutherland.