The Great Game over Sikkim

Tibetan Army at the beginning of the 20th century

The spokesperson of the Chinese Ministry of Foreign Affairs has been vociferously trying to convince the Indian correspondents in Beijing about the 1890 Convention (known as Convention of March 17, 1890 between Great Britain and China relating to Sikkim and Tibet).
However, Beijing forgot to mention about the two main stakeholders, Tibet and Sikkim, who were not even consulted by the 'Great Imperial Powers'.
It is interesting to have the views of Tsepon WD Shakabpa, the Tibetan politician and famous historian.
In his Tibet: a Political History, he explained:

In 1890 a convention was drawn up in Calcutta by Lord Lansdowne, the Governor-General of India and Sheng-t'ai, the Manchu Amban from Lhasa, without consulting the government of Tibet. The first article of the convention agreement defined the boundary between Tibet and Sikkim, and the second article recognized a British protectorate over Sikkim, which gave them exclusive control over the internal administration and the foreign relations of that country.
There was, however, no corresponding acknowledgment on the part of the British of China's authority over Tibet. The remaining six articles related to Tibet, and since she was not represented at the Convention, those articles were not allowed to be put into practice by the Tibetans. The British were aware that China exercised no real power in Tibet at that time; but it suited their interests to deal with the Manchus, because of the advantages they gained from the Convention.
It is also possible that, because of the brief clash between the Tibetans and the British at Lungthur [see note below], the Manchus were afraid that Tibet and Britain might enter into direct negotiations; they therefore agreed to a Convention to forestall such a possibility.
An addition was made to the Convention, known as the Trade Regulations of 1893, in which the question of increasing trade facilities across the Sikkim-Tibet frontier was discussed. Again, the provisions of that agreement could not be enforced because Tibet had not been a party to the negotiations. It is surprising that the British entered into a second agreement with the Manchus, when they knew from the results of the first agreement that there was no way of putting the agreement into effect. The Manchus had signed on behalf of the Tibetans; yet they were totally unable to persuade or force them to carry out the provisions of the agreement. A Tibetan, Lachag Paljor Dorje Shatra, was sent to Darjeeling to study the situation. He sent valuable reports to Lhasa; but they did not meet with the favor of the government, which still believed that too close a contact with the British would damage the Tibetan way of life and religion.
About that time, a Japanese monk, Ekai Kawaguchi, under the pretext of being a Ladahki monk, was enrolled for studies at the Sera monastery. He was delivering inaccurate information to the British in India through Sarat Chandra Das. Those inaccurate reports led the British to believe that Tibet was receiving military aid in the form of "small firearms, bullets, and other interesting objects" from Russia.
Moreover, Kawaguchi estimated that there must have been over two hundred Buriat students in the major monasteries of Tibet. The increasing fear of the establishment of Russian influence in Tibet, which would constitute a grave danger to India, led the British to realize that they could no longer deal with Tibet through China; but that they must attempt to establish direct contact with the Lhasa government.
The fact that the Convention of 1890 and the Trade Regulations of 1893 proved in practice to be of not the slightest use was because Tibet never recognized them. Francis Younghusband quotes Claude White, the Political Officer of Sikkim, as saying that the Chinese had "no authority whatever" in Tibet and that "China was suzerain over Tibet only in name".

Note on Lungthur:
In 1887, a fortified post was built by the Tibetans in Lungthur in North Sikkim, which according them, was inside their territory. Unfortunately the British did not agree with the demarcations and demanded their immediate removal.
An ultimatum was sent to the Tibetan commanders to vacate their fortifications before March 15, 1888. At the same time the British sent a formal protest which was forwarded to the Manchus and the Dalai Lama by the Choegyal.
Though not in a position to intervene, the Manchus told the British that “no marked separation existed formerly between Tibet and Sikkim” and that the Tibetans regarded the kingdom of Sikkim as an extension of their own country.
The Kashag (Cabinet of Ministers) replied to the Choegyal that there was no harm if Tibet defended its own borders. This time the British were not in a mood to discuss or even negotiate the exact position of the border.
With the pressure mounting, the British positioned more than 2,000 troops of the Sikkim Field Force. The Tibetans sent 900 men as reinforcement under two generals and a minister, Kalon Lhalu.
Till the last minute the Choegyal tried to mediate, but each party was determined to show the other that they were within their rights. Unfortunately for the Tibetans, their troops were no match for the British, neither in training, equipment nor discipline. The clash which took place at Lungthur was short and the Tibetans were trounced.

Where is Gipmochi?
Article 1 of the 1890 Convention states:

The boundary of Sikkim and Tibet shall be the crest of the mountain range separating the waters flowing into the Sikkim Teesta and its affluents from the waters flowing in to the Tibetan Mochu and northwards into other rivers of Tibet. The line commences at Mount Gipmochi on the Bhutan frontier, and follows the above-mentioned water-parting to the point where it meets Nepal territory. The boundary of Sikkim and Tibet shall be the crest of the mountain range separating the waters flowing into the Sikkim Teesta and its affluents from the waters flowing in to the Tibetan Mochu and northwards into other rivers of Tibet. The line commences at Mount Gipmochi on the Bhutan frontier, and follows the above-mentioned water-parting to the point where it meets Nepal territory.

According to Sikkimese records, Gipmochi is Batang La, 5 km north of Doka La.
It means the territory South of Batang La is Bhutanese, therefore India did not 'trespass' into Tibet.
All this fuss for nothing?