Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| AGR Power Station | Net MWe | Construction started | Connected to grid | Commercial operation | Accounting closure date |
| --- | --- | --- | --- | --- | --- |
| Dungeness B | 1110.0 | 1965.0 | 1983.0 | 1985.0 | 2018.0 |
| Hartlepool | 1210.0 | 1968.0 | 1983.0 | 1989.0 | 2019.0 |
| Heysham 1 | 1150.0 | 1970.0 | 1983.0 | 1989.0 | 2019.0 |
| Heysham 2 | 1250.0 | 1980.0 | 1988.0 | 1989.0 | 2023.0 |
| Hinkley Point B | 1220.0 | 1967.0 | 1976.0 | 1976.0 | 2023.0 |
| Hunterston B | 1190.0 | 1967.0 | 1976.0 | 1976.0 | 2023.0 |
Question:
What year did construction start at Heysham 1
Answer:
1970.0