“Our willingness to sell reflects the value of the offer,” Ivan Glasenberg, Glencore Xstrata chief executive, said on Sunday, as the trader-cum-miner finally let go of one of the world’s largest copper mines in development – Las Bambas in Peru. Willingness: not requirement. Glencore may have an offer of more than $6bn in cash, from a Chinese consortium. But the choice of phrase shows Glencore always had the ability to keep Las Bambas.

The offer is higher than many expected, and Glencore has also agreed to sell months before it had to, in a process begun as a condition for China’s approval of the Xstrata merger. But “de-risking” Las Bambas (such as putting in infrastructure) made it more viable to keep as well as making it more valuable to the Chinese buyers. Each year, 450,000 or so tonnes of high-quality copper production from Las Bambas could have generated $1.5bn in cash for Glencore, Investec estimates.

However, that point would be several years away. Before then Las Bambas requires heavy capital spending to develop ($400m in the first three months of 2014 alone, which the consortium will also pay for). Keeping rating agencies at bay also takes priority given Glencore’s debt is high ($35bn, even after netting off trading inventories). Glencore’s BBB rating might be shored up if (say) a third of the Las Bambas cash is used to cut debt.